Q. 13 For any two languages L1 and L2 such that L1 is context free and L2 is recursively enumerable but not recursive, which of the following is/are necessarily true?
1. L1' (complement of L1) is recursive 2. L2' (complement of L2) is recursive 3. L1' is context-free 4. L1' ∪ L2 is recursively enumerable
(A) 1 only
(B) 3 only
(C) 3 and 4 only
(D) 1 and 4 only
Answer: (D)
Explanation:
