56.

Answer and Explanation

Your Answer is

Correct Answer is H

Explanation

Analysts thought is a complete sentence after the comma, so a master-slave conjunction is needed in front, so F is wrong. Judging from the meaning, "Because the beams and plates seem to be well preserved, analysts believe that the remainder of the left hull is relatively complete and preserved by depth and coolness." The two sentences are causal, so use since.