With some technical problems to be solved, it may be a while the system is put into use.
A. when
B. after
C. since
D. before
网友回答
A. when
B. after
C. since
(答案→)D. before
解析:考查连词辨析。When当什么的时候,after 什么之后,since自从,before 在什么之前,才,就,句意:有许多技术问题要被解决,可能过一会系统才能被使用。所以选D。