一枚火箭由地面竖直向上发射，其速度和时间的关系图线如图所示，则

A．t₃时刻火箭距地面最远

B．t₂—t₃的时间内，火箭在向下降落

C．t₁—t₂的时间内，火箭处于失重状态

D．0—t₃的时间内，火箭始终处于超重状态

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