第9题: [单项选择]抽滤操作过程中,停止时应()。 A. 先关水泵,再让吸滤瓶通大气 B. 先让吸滤瓶通大气,再关水泵 参考答案:B
第10题: [单项选择]We have ( ) a number of our customers in this area and ninny of them take an interest in your products. A. contacted B. contacted with C. been contacted with D. in contact with 参考答案:A