最常见的引起白瞳症的眼病是（）。

A.Coats病

B.永存原始玻璃体增生症

C.白内障

D.早产儿视网膜病变

E.转移性眼内炎

To keep injured survivors warm in the water after abandoning a ship，they should（）.

A.be placed in the middle of a small circle formed by the other survivors in the water

B.float on their backs with their arms extended for maximum exposure to the air

C.remove their life preservers and hold on to the uninjured survivors

D.sip seawater at intervals of fifteen minutes