Multiple choice

Let L1 be a recursive language. Let L2 and L3 be languages that are recursively enumerable but not recursive. Which of the following statements is not necessarily true?

  1. L2 - L1 is recursively enumerable

  2. L1 - L3 is recursively enumerable

  3. L2 $\cap$ L1 is recursively enumerable
  4. L2 $\cup$ L1 is recursively enumerable
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation