Question

the sun rises in the east and sets in the west , so it seems as if the sun____ round the earth

请高手解释 为什么选择 were circling 不选circles

Answer 1

as if后一般用虚拟语气：1,.与现在事实相反用过去式（be动词用were），本质上讲就是原来的时态退后一格，此处就是这情况，本来应the sun circles round the earth.（退一格即circled）或The sun is circling round the earth,用进行时态更有动态的感觉，（退一格即were circling,注意be动词用were),故此题选A，但就语法而言B也是正确的，只是A更形象生动。
2.与过去相反 had done （本质上讲也是原来的时态退后一格）3.与将来相反would/could/..do
另外若是很可能出现的情况或是事实，也可用正常时态，如It seems as if it's going to rain.

Answer 2

as if引导的从句用虚拟语气，表示同时或将来的情况，动词要用过去式（be动词用were）。本句话中指的是说话当时的情况，所以要用过去式，故were circling是正确答案。