Many of the activities performed during the preliminary investigation are still being conducted in (1) , but in much greater depth than before. During this phase, the analyst must become fully aware of the (2) and must develop enough knowledge about the (3) and the existing systems to enable an effective solution to be proposed and implementeD. Besides the (4) for process and data of current system, the deliverable from this phase also includes the (5) for the proposed system.

5（）

A．hardware and software specification

B．system performance specification

C．formal requirements definition

D．general problem statement

地球内部圈层的划分依据是：（）

A.岩浆组成物质不同

B.岩浆比例的不同

C.各层的厚度不同

D.地震波传播速度的突然变化