(二) 根据下面一段话的内容，从方框内的7个选项中选出能填入空白处的最佳选项，其中有两项为多余选项 A: Excuse me.（16）B: Yes. You don’t know me, of course. I don’t teach here. I just give oral examinations here now and then. Don’t be nervous. A: Nervous Who Me B: （17）I’m going to ask you a few questions. Then we are going to have a short conversation in English. Do you understand A: Yes, of course I do. （18） B: After the examination, please. First of all, why are you learning English A: Why am I learning English B: Yes, I mean, what are you going to do with it Are you going to be a teacher of English, or what else A: （19）I really must ask you something first. B: Very well. If you insist, go ahead please! A: Would you like a cup of coffee B: Pardon What did you say A: You see, I’m English. I’m one of the teachers here. I came to ask you if you would like a cup of coffee. B: （20）. And thank you so much!

第五空应选择（）

A．You must have wronged me.

B．Oh! I’m so sorry about this.

C．Please stop just a second.

D．Are you Mr.Smith

E．But may I ask you something first

F．Is there anything I can do for you

G．Now. Sit down, please.

在反应3BrF₃+5H₂O=HbrO₃+Br₂+9HF+O₂中，如果有5个水分子发生反应，化合价升高的分子总数和化合价降低的分子总数之比为（　　）

A．3：1

B．3：2

C．3：5

D．5：3