Question

Which of the following is a regular language?

(a) String whose length is a sequence of prime numbers

(b) String with substring ww^r in between

(c) Palindrome string

(d) String with even number of Zero’s

I had been asked this question by my college director while I was bunking the class.

This interesting question is from The Language of NFA topic in portion Finite Automata of Automata Theory

Answer 1

The correct answer is (d) String with even number of Zero’s

Explanation: DFSM’s for the first three option is not possible; hence they aren’t regular.