Question

If the strings of a language L can be effectively enumerated in lexicographic (i.e., alphabetic) order, which of the following statements is true?

• A. L is regular but not necessarily finite
• B. L is context free but not necessarily regular
• C. L is recursive but not necessarily context free
• D. L is necessarily finite

Answer 1

The correct option is C L is recursive but not necessarily context free

Theorem: A language is recursive if and only if it can be effectively enumerated in lexicographic order.
Based on this theorem clearly the answer is (d).