From your reading of the passage, which of the following is tree

A．At a depth of 1,200 feet the effects of a violent surface storm are frightful.
B．A submarine commander navigating his vessel at a depth of 700 feet will not be affected by a ranging surface storm.
C．A typhoon 500 miles out at sea can stir up the ocean floor.
D．If high waves can strike the shore with a horizontal force of 75 million pounds, the vertical force of such waves can have an even greater effect upon the ocean floor.