.Three-fourths of the surface of the earthsea.A. isB. areC. wereD. has been

问题补充：

.Three-fourths of the surface of the earthsea.

A. is

B. are

C. were

D. has been

答案：

(答案→)A. is

B. are

C. were

D. has been

解析：本题的含义是地球表面的四分之三是海洋，表示的是一个客观的事实用一般现在时，本题的主语为不可数名词，故用is，故本题选A。