— ____ in this street?   — I think Mr. Black is the richest man.

A．Whom do you think is the richest man

B．Who do you think is the richest man

C．Do you think who is the richest man

D．Do you think whom is the richest man

When jumping into water upon which there is an oil-fire，you should（）.

A.break the water surface with your hands when diving head-first

B.use your hands to hold your knees to your chest

C.cover your eyes with one hand while pinching your nose shut and covering your mouth with the other

D.enter the water at the bow or stern on the windward side of the vessel