Tom Williams, _____scientist of the British Association for the Advancement of Science, is one of _____ kind of persons who can give you _____ hand whenever you are in trouble.

A．a / a / a

B．a / the / a

C．the / a / a

D．the / the / the

下列叙述不正确的是         （   ）

A．含有金属元素的晶体不一定是离子晶体

B．原子晶体中只存在共价键

C．HF、HC1、HBr、HI四种物质的沸点依次升高

D．金属晶体之所以能导电是因为其中含有自由移动的电子