三七的止血有效成分为
A．三七皂苷
B．三七氨酸
C．三七黄酮A
D．齐墩果酸型皂苷
E．三七黄酮B
参考答案：B
日常生活中喝牛奶能补钙，这里的“钙”指的是（ ）
A．元素
B．原子
C．分子
D．离子
— Jack! You are wet through. Didn't you listen to the weather report this morning?
— No, I didn't. I was in a hurry. Besides, it ______ when I left. [ ]
A．was raining
B．wasn't raining
C．would rain
D．Hadn't rained
