下列实验操作正确的是 [ ]
A．用天平称食盐
B．稀释浓硫酸
C．检查气密性
D．过滤
答案：C
My goodness. How lucky we are! If there had been places for us on that aero-plane, we ________dead now.
A．will be
B．would be
C．would have been
D．had been
喷氨阀的根部在何处，在什么样的情况下使用？
用天平称食盐 
稀释浓硫酸 
检查气密性 
过滤
用天平称食盐 稀释浓硫酸 检查气密性 过滤