下列说法正确的是（   ）

根据对话语境，在空白处填写恰当的句子补全对话
A: Good morning!
B: Good morning! I’d like to join the school volunteer project, but____ .
A: OK, don’t worry. Let me help you.____ ?
B: I love singing and telling stories.
A: Well, you could help look after young children on weekends.
B: ____ . I can sing for them and tell them stories. I’m sure that  children will love me.
A: I agree with you. ____ ?
B: Sure. I am Peter White. My telephone number is 885-276.
A: OK. I’ll call you as soon as possible.
B: ____ .
A: It’s my pleasure.

北京是全国的（　　）

阅读文言文《虹》，完成后面小题。
       世传虹能入溪涧^①饮水,信然^②。熙宁^③中,余使契丹^④，至其极北黑水境永安山下卓帐^⑤。是时新雨霁^⑥，见虹下帐前涧中。余与同职扣^⑦涧观之，虹两头皆垂涧中。使人过涧，隔虹对立，相去数丈，中间如隔绡穀^⑧。自西望东则见，盖夕虹也。立涧之东西望，则为日所烁^⑨，都无所睹。久之，稍稍正东，逾^⑩山而去。次日，行一程，又复见之。孙彦先^⑪云：“虹乃雨中日影也，日照雨即有之。”                       
                                                                                                                                       （选自《梦溪笔谈》）
     【注】①溪涧：溪流、山涧。②信信：确实如此。③熙宁：宋神宗赵项年号，公元1068—1077年。④契丹：宋时北部少数民族政权。⑤至其极北黑水境永安山下卓帐：到了极北方黑水境内的永安山下建起帐篷。卓帐：竖起帐篷。⑥新雨霁：刚好雨后初晴。⑦扣：靠近。⑧绡穀：生丝织成的薄纱。⑨烁：闪烁。⑩逾：越过。⑪孙彦先：与沈括同时代的科学家。