检查加氯系统泄漏的正确方法是()。
A、观察是否有无色无味的气体
B、观察是否有黄绿色的气体
C、用氨水试漏,观察是否有有白色烟雾
D、用手扇微量气体是否有刺激性气味
参考答案:C
— Sorry, sir, your car isn't ready yet. It ____ by our workers.
— Oh, my God, when can I come to fetch it? [ ]
A. is repaired
B. has been repaired
C. is being repaired
D. will be repaired
市场竞争可以分为三种行为:()、()和()。