考虑以下语句：
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 以上哪些陈述是/是正确的?
(A)只有 2 个
(B)只有 3 个
(C)只有 1 和 2
(D)只有 1 和 3答案： (D)
解释：
1 is true: Complement of Turing decidable is Turing Decidable.
3 is true. All NP problems are Turing decidable
(See https://www.geeksforgeeks.org/np-completeness-set-1/)
2 is false: The definition of NP itself says solvable in
polynomial time using non-deterministic Turing machine. 这个问题的测验