Q. 78 Which of the following are decidable?
1. Whether the intersection of two regular languages is infinite 2. Whether a given context-free language is regular 3. Whether two push-down automata accept the same language 4. Whether a given grammar is context-free
(A) 1 and 2
(B) 1 and 4
(C) 2 and 3
(D) 2 and 4
Answer: (B)
Explanation:
