以下气体是哪一组属于煤矿是常见的有毒气体（）
A.CO和H2S
B.CH4和NO2
C.CO2和H2
参考答案：A
热凝塑料最佳填塞期是（）
A.湿砂期
B.稀糊期
C.粘丝期
D.面团期
E.橡胶期
Speaker A: I think Jack needs to go on a diet. He's putting on so much weight.Speaker B: ______
A．Yes, he used to be overweight.
B．Yes, I don't think highly of him.
C．How much do you think he actually weighs now
D．Do you think so I think he looks OK the way he is.
