《芝加哥公约》最初签定于()年。
A.1919
B.1944
C.1945
D.1947
参考答案：B
题11图所示电路的等效电阻Rab为( )
A．10
B．20
C．30
D．40
I will stay at home if my aunt _____ to visit us tomorrow.[ ]
A. will come
B. is coming
C. came
D. comes
