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
网友回答
A. why
B. how
(答案→)C. because
D. whether
解析：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，如: She was ill. That’s why she was sent to the hospital. 她病了，所以被送到医院来(那就是她为什么被送到医院的原因)。Because引导表语从句强调原因,结合语境可知选C.
【考点定位】连词辨析