题目内容
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 |
C
解析试题分析：考查连接词：Why为什么;how怎样, 如何;because因为;whether是否. 句意:从太空中望去, 地球看起来是蓝色的. 这是因为它的表面大约百分之七十被水覆盖. Why在引导表语从句时强调结果， Because引导表语从句强调原因,结合语境可知选C.
考点：考查连接词
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