上体育课时为了安全，应该（）
A、穿紧身衣
B、衣服上不别别针
C、带好钥匙
D、穿拖鞋
参考答案：B
If you had joined the chat room ten minutes ago, you _____________what we were talking about.
A．would know
B．would have known
C．knew
D．had known
一般站调整为国家气象观测一级站的，台站类别正确的修改方式为（）.
A.一般站→国家气象观测站
B.一般站→国家气象观测一级站
C.一般站→基本站
D.不用修改
