下图为人体血液内氧气和二氧化碳含量的变化曲线，请据图回答。（图中H为肺动脉）

（1）曲线a表示的是__________在血液中含量的变化；曲线b表示的是__________在血液中含量的变化。

（2）I代表的血管是_______    ___，J代表的血管是____      ______。

（3）曲线b在I段血管处迅速升高是由于_____           ______。

（4）曲线b所表示的气体在血液内主要存在的方式是____    _____。

根据下面一段对话内容，从方框内的7个选项中选出最佳选项。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 MeB: ____17____ I’m going to ask you a few questions. Then we are going to have a short conversation in English. Do you understandA: Yes, of course I do. ____18____ B: After the examination, please. First of all. why are you learning EnglishA: Why am I learning EnglishB: Yes, I mean, what are you going to do with it Are you going to be a teacher of English, or what elseA: ____19____ I really must ask you something first.B: Very well. If you insist, go ahead please!A: Would you like a cup of coffeeB: PardonWhat did you sayA: 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!

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.