Having tried hard several times, they finally _____ the hope of finding an effective way to save the dying man. [ ]

A. abandoned

B. released

C. discouraged

D. resigned

电压互感器的一次侧装保险（熔断器）是用来（）。

A.防止电压互感器二次过负荷的影响

B.防止电压互感器烧毁

C.防止高压电网受电压互感器本身或其引线上故障的影响