一般现在时与现在完成时辨析 — 英语选择题
题目
选择最佳选项填空：China's Shenzhou astronauts ___ daily exercise routines to keep fit in microgravity, and since the space station was completed, they ___ more than ten science experiments aboard it. A. do; have completed B. have done; complete C. did; completed D. are doing; complete