语音知识（共5小题；每小题1分，满分5分）

1. shocked                 A. finished                  B. prevented             C. paused                   D. doubled

2. produce (n.)      A. spot                        B. protective             C. production   D. fault

3. Christian           A. Christ                     B. Christmas             C. patient                   D. suggestion

4. great                  A. scene                     B. steak                      C. weakness    D. seek

5. wonder              A. southern               B. wander                  C. protein                   D. flavour

对直流系统应进行哪些巡视检查项目？