安防系统的运行保障包括：（）、运行维护、运行维护主要管理制度。
A、故障修理
B、报警响应
C、设备检查
D、签订维保合同
参考答案：B
My brother has _____ in Japan. [ ]
A. pen pal
B. a pen pal
C. two pen pal
D. a pen pals
— Do you know where David is? I couldn't find him anywhere.
— Well. He _____ have gone far-his coat is still here. [ ]
A. shouldn't
B. mustn't
C. can't
D. wouldn't
