甘醇类化合物吸水性很强，溶液冰点较低，居主导地位。目前常采用三甘醇。Ethylene glycol compounds have strong water absorption and low freezing point of solution. Triethylene glycol is commonly used at present.

规模经济存在时,A.B.

单项选择题规模经济存在时,

在地球大气层的5层中，大气处于高度电离状态的分层是 。A、对流层B、热层C、平流层D、中间层

单项选择题在地球大气层的5层中，大气处于高度电离状态的分层是 。

When the teacher corrects students’ mistakes in class, ...

判断题When the teacher corrects students’ mistakes in class, he or she is using English for real communication.