膨胀机产冷效果下降的因素是（）
A、机前使用节流
B、机后压力升高
C、喷嘴开度小
D、机前压力不变，机后压力降低
参考答案：C
— Could you help me do some cleaning after school?
— If I _______, I will do it.
A．am free
B．will be free
C．have had time
D．had time
试述稽查进点会谈的主要内容？
