Final answer:
Reductions from 2-SAT to 3-SAT are possible in polynomial time, 2-SAT is in class P, and k-SAT is in class NP for any k>1; 3-SAT to 2-SAT reduction's existence would imply P=NP.
Step-by-step explanation:
The question involves understanding concepts from computational complexity theory, specifically polynomial time reduction and complexity classes such as P and NP. The true statements are:
- There is a polynomial time reduction from 2-SAT to 3-SAT. (True)
- 2-SAT is in the class P. (True)
- For any natural number k>1, k-SAT is in the class NP. (True)
There is no known polynomial time reduction from 3-SAT to 2-SAT because 3-SAT is NP-complete, and such a reduction would imply that P=NP, which is a major unsolved question in computer science.