下列关于H₂O₂、H₂、H₂O三种物质组成的叙述正确的是（　　）

A．都含有氢元素

B．都含氢气

C．都只有两个氢原子

D．都含一个氢分子

An expert system is a software that (41) specialist knowledge-about a particular domain of (42) and is capable of making (43) decisions with in that domain. Although expert systems typically focus on a very narrow domain, they have achieved dramatic success with (44) problems, This has excited wide spread interest outside the research laboratories from which they emerged.
Expert systems have given rise to a set of "knowledge engineering" methods constituting a new approach to design of high performance software system. This new approach represents an (45) change with revolutionary consequences.

A．develops

B．directory

C．effect

D．encapsulates

E．evolutionary

F．experienced

G．expertise

H．intelligent

I．real-life

J．real-time