With a lot of tough problems       , the pilot was still calm, cool and collective under pressure.

A．solve

B．solved

C．solving

D．to solve

变电站计算机监控系统的检修维护工作按工作内容和性质可分为（）

A.测试检查

B.故障检修

C.临时检修

D.计划检修

E.缺陷检修