选用方框中的句子完成对话，其中有两项是多余的。
Li Lei: Excuse me. ____
Mr. Smith: Yes. And you are.. . ?
Li Lei: I’m Li Lei. Your friend Miss Wu is busy at the moment. She asks me to meet you. Welcome to Hangzhou, Mr. Smith.
Mr. Smith: Thank you.
Li Lei: By the way____ 
Mr. Smith: No. This is my second time. I came here in 1998 for the first time.
Li Lei:____
Mr. Smith: I like it very much. It’s very beautiful and famous in the world. And the people here are quite friendly.____
Li Lei: I’m glad you like the city. And now Hangzhou is becoming more and more beautiful.____
Mr. Smith: I think so. Thank you very much for meeting me.
Li Lei: It’s a pleasure.

如图，AB和CD分别是⊙O上的两条弦，过点O分别作ON⊥CD于点N，OM⊥AB于点M，若ON=$\frac{1}{2}$AB，证明：OM=$\frac{1}{2}$CD．

有20个同学排成一行，若从左往右隔1人报数，小李报8号；若从右往左隔2人报数，小陈报6号．那么，从小陈开始向小李逐人报数，小李报的号数为(  )．

极昼和极夜现象与____、____和____有关。