Let G = (V;E) be a connected, undirected graph, and let a and b be two distinct vertices in V . Let P1 be the problem of finding a shortest simple path between a and b, and P2 be the problem of finding a longest simple path between a and b. Which of the following statements about P1 and P2 is true?

A. Both P1 and P2 can be solved in polynomial time.

B. P1 can be solved in polynomial time but P2 is not known to be solvable in polynomial time.

C. P1 is not known to be solvable in polynomial time but P2 can be solved in polynomial time.

D. It is not known whether either P1 or P2 can be solved in polynomial time.

E. It is known that neither P1 nor P2 can be solved in polynomial time.