MCQs

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Overall MCQs for Reference

Which symbol in regular expressions denotes zero or more occurrences of the preceding element?
a. +
b. *
c. ?
d. $
Answer: b. *testbook
What regular expression represents all strings starting with ‘a’ over the alphabet {a, b}?
a. a(a+b)
b. a(a+b)*
c. a*
d. a*(a+b)*
Answer: b. a(a+b)*t4tutorials
Which operation are regular expressions closed under?
a. Union
b. Intersection
c. Kleene star
d. All of these
Answer: d. All of theset4tutorials
What does the regular expression ab match?
a. All strings consisting of any number of ‘a’s followed by any number of ‘b’s
b. All strings starting with ‘a’ and ending with ‘b’
c. Only strings that alternate between ‘a’ and ‘b’
d. Only the empty string
Answer: a. All strings consisting of any number of ‘a’s followed by any number of ‘b’stestbook
Which type of machine accepts regular languages?
a. DFA
b. PDA
c. LBA
d. Turing machine
Answer: a. DFAsanfoundry
What does the regular expression ab* represent?
a. One ‘a’ followed by zero or more ‘b’s
b. Zero or more ‘a’s followed by one ‘b’
c. Any string containing ‘ab’
d. Only the string “ab”
Answer: a. One ‘a’ followed by zero or more ‘b’st4tutorials
In regular expressions, what does the symbol “|” denote?
a. Concatenation
b. Union
c. Intersection
d. Complement
Answer: b. Uniont4tutorials
Which regular expression matches all strings ending with ‘b’?
a. (a+b)b
b. b(a+b)
c. (ab)
d. (b*)a
Answer: a. (a+b)*bt4tutorials
What is the regular expression for strings containing only even number of ‘a’s?
a. (baba)*
b. (baa)
c. (a+b)*
d. (aabb)*
Answer: b. (baa)scribd
For digit extraction, which regular expression segment denotes any four digits?
a. d{4}
b. \d{4}
c. [0-9]{4}
d. (0-9){4}
Answer: b. \d{4}librarycarpentry.github
What does the regular expression [A-Za-z]+ match?
a. All digit strings
b. All non-alphabet strings
c. All alphabetic strings
d. All symbols
Answer: c. All alphabetic stringslearn.microsoft
Which is a valid regular expression for matching consecutive a’s over {a, b}?
a. (aa+b)
b. aa(b)*
c. (aa+b)*
d. None of these
Answer: c. (aa+b)*t4tutorials
What is Kleene star in regular expression?
a. Repetition zero or more times
b. Repetition exactly once
c. Optional inclusion
d. Grouping operation
Answer: a. Repetition zero or more timestestbook
Choose the regular expression for where every ‘a’ in a string is tripled.
a. aaa*
b. (aaa+b)*
c. (a+aa)*
d. (b+aaa)*
Answer: b. (aaa+b)*scribd
Which regular expression denotes an empty string?
a. ∅
b. ε
c. a*
d. (a+b)*
Answer: b. εcesaraguilar.weebly
What regular operation is not supported in basic regular expressions?
a. Union
b. Intersection
c. Kleene star
d. Concatenation
Answer: b. Intersectiont4tutorials
How many strings of length 3 does (a+b)* generate?
a. 6
b. 8
c. 9
d. 12
Answer: b. 8sanfoundry
Match the following: Lexical analysis is commonly implemented using:
a. Regular expressions
b. Pushdown automata
c. Turing machines
d. Context-free grammars
Answer: a. Regular expressionstestbook
Which string does not match with aa(bb)*?
a. aabb
b. aabbbb
c. aa
d. ab
Answer: d. abt4tutorials
Which method is used in Python to find all occurrences of a pattern in a string using RegEx?
a. match()
b. findall()
c. search()
d. check()
Answer: b. findall()geeksforgeeks
Which regular expression matches strings containing at least two consecutive ‘b’s?
a. b{2,}
b. bb
c. (bb)+
d. All of the above
Answer: d. All of the abovelearn.microsoft
The regular expression (a+b)b(a+b) defines:
a. Strings where ‘b’ appears at least once
b. Strings ending with ‘b’
c. Strings starting with ‘b’
d. Strings with only ‘a’
Answer: a. Strings where ‘b’ appears at least oncet4tutorials
Which operation is not possible using regular expressions?
a. Backreferencing
b. Union
c. Kleene closure
d. Concatenation
Answer: a. Backreferencinglearn.microsoft
In AI chatbot ELIZA, regular expressions were used for:
a. Parsing user input
b. Memory management
c. Network security
d. System calls
Answer: a. Parsing user inputcesaraguilar.weebly
What does the regular expression (xyz)? match?
a. ‘xyz’ repeated zero or more times
b. No occurrence or one occurrence of ‘xyz’
c. Every string containing ‘xyz’
d. Only empty string
Answer: b. No occurrence or one occurrence of ‘xyz’learn.microsoft
Regular expressions can be converted to which type of automata?
a. Deterministic finite automata (DFA)
b. Pushdown automata (PDA)
c. Turing machines
d. Linear bounded automata
Answer: a. Deterministic finite automata (DFA)sanfoundry
The regular expression (a|b)* matches:
a. Any string over {a, b}
b. Only strings with alternating a and b
c. Only the empty string
d. Only the string “ab”
Answer: a. Any string over {a, b}t4tutorials
Which regular expression matches the string “hello”?
a. hello
b. h+e+l+l+o+
c. .hello.
d. [hello]
Answer: a. hellolearn.microsoft
Which of the following is true regarding regular expressions?
a. Defines regular languages
b. Can model context-sensitive languages
c. Defines context-free languages
d. Can represent every recursively enumerable language
Answer: a. Defines regular languagest4tutorials
The regular expression [0-9]{3} matches what?
a. At least three digits
b. Exactly three digits
c. Three alphabetic characters
d. Any digit
Answer: b. Exactly three digitslibrarycarpentry.github
The “+” operator in regular expressions means:
a. One or more occurrences of preceding element
b. Zero or more occurrences
c. Exactly one occurrence
d. Match all elements
Answer: a. One or more occurrences of preceding elementlearn.microsoft
Which regular expression denotes strings that contain ‘cat’ or ‘dog’?
a. (cat|dog)
b. [catdog]
c. cat&&dog
d. cat+dog
Answer: a. (cat|dog) learn.microsoft
What is the regular expression for all strings not containing ‘ab’?
a. ((a+b)* – ab)
b. (a*|b*)
c. (ba)
d. (a+b)* without ab
Answer: d. (a+b)* without ablearn.microsoft
What does “(abc)*” represent?
a. Only the empty string
b. Any number of occurrences of “abc”
c. Only one “abc”
d. Strings of a, b, or c
Answer: b. Any number of occurrences of “abc”learn.microsoft
Which of these is not a regular language?
a. Strings with equal number of a’s and b’s
b. Strings ending in ‘ab’
c. Strings containing only ‘a’
d. Strings with only even number of b’s
Answer: a. Strings with equal number of a’s and b’ssanfoundry
The regular expression “a?b*” matches:
a. Zero or one ‘a’, followed by zero or more ‘b’s
b. At least one ‘a’ and one ‘b’
c. Only ‘bb’
d. Only ‘a’
Answer: a. Zero or one ‘a’, followed by zero or more ‘b’slearn.microsoft
Which regular expression matches all strings of exactly two characters over {a, b}?
a. (a+b)(a+b)
b. (a+b)*
c. a?b?
d. a+b+
Answer: a. (a+b)(a+b)learn.microsoft
What does the regular expression “^abc” match?
a. ‘abc’ anywhere in the string
b. ‘abc’ at the start of the string
c. ‘abc’ at the end of the string
d. None of these
Answer: b. ‘abc’ at the start of the stringlearn.microsoft
Which regular expression denotes all strings over {0,1} that do not contain ’11’?
a. (0+1)* – 11
b. (010)*
c. (101)*
d. (0+1)* without 11
Answer: d. (0+1)* without 11learn.microsoft
Regular expressions in natural language processing are primarily used for:
a. Pattern matching
b. Model training
c. Data normalization
d. Feature extraction
Answer: a. Pattern matchingcliffsnotes
What is the significance of parentheses in regular expressions?
a. Precedence and grouping
b. Repetition
c. Wildcard matching
d. Concatenation
Answer: a. Precedence and groupinglearn.microsoft
What regular expression matches any string not containing the letter ‘z’?
a. [^z]*
b. [z]*
c. z*
d. .z.
Answer: a. [^z]*learn.microsoft
Which regular expression matches an email address?
a. [A-Za-z0-9.%+-]+@[A-Za-z0-9.-]+.[A-Za-z]{2,}
b. @email
c. ([email]+)
d. \d*@\d*
Answer: a. [A-Za-z0-9.%+-]+@[A-Za-z0-9.-]+.[A-Za-z]{2,}learn.microsoft
Which function in JavaScript tests a regular expression against a string?
a. test()
b. check()
c. find()
d. match()
Answer: a. test()learn.microsoft
The regular expression ‘^\d{3,}$’ matches:
a. Strings with at least 3 digits at the start
b. Strings with exactly 3 digits
c. Any digit
d. Digits in the middle only
Answer: a. Strings with at least 3 digits at the startlearn.microsoft
Which regular expression matches strings containing only uppercase letters?
a. [A-Z]+
b. [a-zA-Z]
c. [A-Z]*
d. [A-Z]{2,}
Answer: a. [A-Z]+learn.microsoft
For matching whitespace, the regular expression symbol is:
a. \s
b. \w
c. \d
d. \t
Answer: a. \slearn.microsoft
Which regex matches a string with exactly six word characters?
a. \w{6}
b. .{6}
c. \d{6}
d. [a-z]{6}
Answer: a. \w{6}learn.microsoft
What is the output of re.findall(r'[ab]{2,}’, ‘ccaaaabbabbb’)?
a. [‘aaaa’, ‘bb’, ‘abbb’]
b. [‘cc’, ‘aaa’]
c. [‘ab’]
d. [‘bbb’]
Answer: a. [‘aaaa’, ‘bb’, ‘abbb’]geeksforgeeks
Which regex finds dates in the format DD/MM/YYYY?
a. \d{2}/\d{2}/\d{4}
b. fd/mm/yyyy
c. [date]+
d. dd/mm/yyyy
Answer: a. \d{2}/\d{2}/\d{4}learn.microsoft

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