若每一条指令都可以分解为取指、分析和执行三步。已知取指时间t_取指=4△t，分析时间t_分析=3△t，执行时间t执行=5△t。如果按串行方式执行完100条指令需要 (4) △t。如果按照流水线方式执行，执行完100条指令需要 (5) △t。

（4）处应填（）

A．1190

B．1195

C．1200

D．1205

The large size and roughly circular shape of the Pacific made some scientists think that it （） a hole left when the moon separated from the earth.

A. used to be

B. would have been

C. might have been

D. should have been