第7题: [单项选择]离心泵不能在()启动。 A. 进口阀打开后 B. 出口阀打开后 C. 出口阀打开前 D. 灌泵排气后 参考答案:B
第8题: [单项选择]The reason why the mice in Ader's experiment avoided saccharin was that ________. A. they disliked its taste B. it affected their immune systems C. it led to stomach pains D. they associated it with stomach 参考答案:D