国务院常务会议一般()。
A.半月召开一次
B.每月召开一次
C.两月召开一次
D.每季度召开一次
参考答案:B
下列射线中,穿透能力最弱的是()。
A、α射线
B、β射线
C、γ射线
D、中子流
After people have learned that magnets attract things, centuries passed______they took note of the fact that magnets sometimes also repel things.
A.before
B.until
C.after
D.since