Which of the following are useful in proving a language to be regular?
(A) All of these
(B) 1, 3 and 4 only
(C) 2, 3 and 4 only
(D) 3 and 4 only
(B)1, 3 and 4 only
As from the given options, Myhill-Nerode theorem is useful by providing necessary and sufficient condition for proving that a language regular. Pumping lemma is often used to prove that a language is non-regular. Drawing an NFA can be useful to prove a language is regular. Forming a regular expression can also help us prove if it is a regular language