补全对话 。

Mrs Brown= A                           

Salesman= B

A: Good morning!                        

B: Good morning! Can I 1. _____you?

A: Yes, 2. _____ I 3. _____ to          

B: Come this way. Here are 4. _____

buy a sweater.                                

A: How 5. _____ is this white one?     

B: 56 dollars.

A: It's 6. _____ expensive.              

B: 7. _____ about this one?

A: I don't like the 8. _____ Let me      

B: That's cheap.  It's only 20 dollars. 9. _____ a look at that blue one.

A: OK. I'll 10. _____ it.

按蚊叮人率是指1人1个夜晚受到蚊虫叮咬的频率，它不单是媒介按蚊传疟能量计算的一个重要参数，也可以作为按蚊的（）指标。

A、密度

B、吸血趋性

C、吸人血率

D、吸血活动规