电力电缆的基本特性：（）；（）、热性能、耐腐蚀和耐气候性能、老化性能、其他性能。
参考答案：电气性能、力学性能
It's time ________.[ ]
A. play football
B. to go to bed
C. playing games
D. for go to bed
－Who's that at the door?
－_____ may be John. [ ]
A. It
B. Him
C. She
D. This
