In general,a typical （）model is composed ofseveral phases, such as requirements analysis phase, general/detailed design phase, implementation phase, system acceptancetesting phase.

A．waterfall

B．incremental

C．spiral

D．prototyping

吗啡的镇痛作用最适用于（）

A.其他镇痛药无效时的急性锐痛

B.神经痛

C.脑外伤疼痛

D.分娩止痛

E.诊断未明的急腹症疼痛