沉淀反应形成的反应现象( )
A．肉眼可见B．肉眼不可见C．必须用精密仪器测定D．必须染色才可见E．经电泳后可见
参考答案：A
—_____ clean the room?
—No, l can't. I'm very busy. [ ]
A. Are you going to
B. Could you please
C. Must you
D. Do you
除法算式中，被除数和除数同时缩小5倍，商______．
