过滤冷却系统中精滤器的过滤精度为()。
A.10μm
B.20μm
C.30μm
D.40μm
参考答案:A
— Jack bought a new mobile phone the other day.
— _____? That's his third one in just one month. [ ]
A. Had he
B. Did he
C. Does he
D. Has he
What does you brother do?[ ]
A. He works very hard.
B. He is outgoing and friendly.
C. He is a sales assistant.
D. He is tall with curly hair.