Q. 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? (Solved)
1. L2-L1 is recursively enumerable
2. L1-L3 is recursively enumerable
3. L2 intersection L1 is recursively enumerable
4. L2 union L1 is recursively enumerable
- b. L1-L3 is recursively enumerable