5、若的二项展开式中含项的系数是80，则实数a的值为       ．

4、在极坐标系中，是极点，设点，，则三角形OAB的面积为       

3、已知复数z＝－i为纯虚数，则实数a=               。

2、不等式的解集为               。

1、方程的解是               。

5.-You speak English quite well. -__             __

A.I don't think so.       B.You don't say so.  C.No, I don't speak well.    D.Thank you.  

4.-Tom will take care of our cat while we're away. -____

A．Fine, thank you.     B.I'll do it myself.   C.That's very kind of him.     D.It doesn't matter.

3.-Help yourself to some apples.-__   A.I don't like it.     B.Sorry, I can't help it.

C.Never mind.       D.Thank you very much.

2.-Do you mind if I close the window?  -____            __

A.No, I mind.    B.Yes, I don't mind.  C. No, not at all.    D.Yes, I'm afraid not.

 思考题：           
1.-Thank you for your help. -__             ___

A.All right.      B.That's all right. C.That's right.   D.It's very kind of you.