【单选题】Please______the safety seal has not been broken before using this product.
【简答题】居家隔离观察对象主要是哪些人?居家隔离观察时间是多久?
【单选题】下列关于DPCM的量化信噪比的说法,正确的是 。
A.
计算方法与 PCM 的量化信噪比计算没有区别;
【单选题】Before using penicillin, _________.
A.
The doctor should make a careful inquiry about sensitivity
B.
T he patient should be given a skin test
【单选题】Before using your new pressure cooker, read the following______ carefully.
【单选题】Before using the machine, you should read the ______carefully. [ ]
【单选题】Tourists have learnt to make investigations about tour operators before using them.