Whcih of the following is not decidable?

(A) A given string is generated by a given CFG is decidable.
(B) Finiteness of a language generated by a CFG is decidable.
(C) Emptiness of a language generated by a CFG is decidable.
(D) If a language is CFG then its complement is also a CFG is decidable..


Answer: (D)

Explanation: If a language is CFG then its complement is also a CFG is undecidable.
So, option (D) is correct.

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