Consider the following statements:
1. The complement of every Turning decidable language is Turning decidable 2. There exists some language which is in NP but is not Turing decidable 3. If L is a language in NP, L is Turing decidable
Which of the above statements is/are True?
A 
Only 2

Only 3


Only 1 and 2


D 
Only 1 and 3

Explanation:
1 is true: Complement of Turing decidable is Turing Decidable.
3 is true. All NP problems are Turing decidable
(See http://www.geeksforgeeks.org/npcompletenessset1/)
2 is false: The definition of NP itself says solvable in
polynomial time using nondeterministic Turing machine.