题目

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  答案：C下列哪种群落中生活的动物往往有冬眠或者夏眠的生活习性A. 森林 B. 荒漠 C. 草原 D. 苔原