H、D、T、H+可以用来表示( ) A.同一种原子 B.化学性质不同的氢原子 C.氢元素 D.氢的四种核素
The CDs are on sale! Buy one and you get ______ completely free.
Progress______ so far very good and we are sure that the work will be finished on time.
Charles was alone at home, with_______ looking after him.
It is often ______ that human beings are naturally equipped to speak.
I’m sure that your letter will get______ attention. They know you’re waiting for the reply.