Which materials can be thrown into the sea on the nature of them?
A. depended
B. depending
C. to depend
D. depends
网友回答
A. depended
B. depending
C. to depend
(答案→)D. depends
解析：考查主谓一致。本题中的Which materials can be thrown into the sea是一个主语从句，当一个单独的主语从句做主语的时候，谓语动词使用单数的形式。故D正确。