— Spacecraft "Discovery" has failed in the course of launch.

— ________? They have been preparing for the test. [      ]

A. How come  

B. When

C. How  

D. Why not

在“三个代表”中，发展先进生产力是发展先进文化和实现最广大人民根本利益的( )。

A．根本前提
B．一般条件
C．前提条件
D．基础条件