Multiple choice

Which of the following problems are decidable? 1) Does a given program ever produce an output? 2) If L is context-free language, then, is L also context-free? 3) If L is regular language, then, is L also regular? 4) If L is recursive language, then, is L also recursive?

  1. 1,2,3,4

  2. 1, 2

  3. 2, 3, 4

  4. 3, 4
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

CFL’s are not closed under complementation. Regular and recursive languages are closed under complementation.

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