于位温在干绝热过程中具有保守性，因此利用这个特性可以（）.
A.评估气团的性质
B.鉴别气团的性质
C.鉴别不同高度处气团的性质
参考答案：C
— How long _________ in singapore?
— For just the weekend. I’ll be back next Monday morning.
A．have you stayed
B．are you staying
C．did you stay
D．do you stay
31. The farmers wondered if vegetables bring in______crops.
A．as many as
B．as good as
C．as much as
D．as well as
