Question

From space, the earth looks blue. This is    ________  about seventy－one percent of its surface is covered by water.

A．why                 B．how

C．because             D．whether

Answer

C

【解析】

试题分析：考查表语从句。语境中“地球表面约71%被水覆盖”和“从太空上看，地球是蓝色的”之间是因果关系，故用because引导表语从句。

【名师点睛】连接表语从句的连接词有：that, what, who, when, where, which, why, whether, how, whoever，whomever，whichever ，whatever等。还有如because, as if, as though等。解答这类题目，关键在于分析清楚句子结构。通过判断引导词在从句中所作的成分及意义，来选择正确的引导词。