笔石的分支方式有()和()。
参考答案:同分支;后分支
You are too late. The film _ since half an hour ago.
[ ]
A. has begun
B. has been on
C. began
D. had begun
普通干粉灭火剂不可扑救()火灾。
A.E类
B.C类
C.B类
D.A类