1. (2020三下·新沂期中) 读对话，根据上下文或句子意思填空。

A. Thank you   B. Open    C. Good morning    D. on    E. Where's    F. in

A: Good morning, class.

B: , Mr Green.

A: Sit down, please.  your book, please.

B: Yes, Mr Green.

A: your book, Mike?

C: Er...

A: Is it your schoolbag?

C: No, it isn't.

D: Look! It'sthe floor(地板).

C: Oh yes!.