题目

在有云的夜晚，抬头望月，觉得月亮在云中穿行，这时选取的参考系是（） A . 月亮 B . 云 C . 地面 D . 星 答案：B"_____ you've made! But you should work still harder," Dad said to me. [     ]A. What big mistake B. How big mistakes C. What great progressD. How great progress