有关地球大小的描述，正确的是[ ]

 A、地球表面积5.1亿平方千米

B、地球赤道周长6371千米

C、地球平均半径4万千米

D、地球公转周期为一天

根据上下文补全对话，在横线上写出所缺少的内容。

Jack: Hello, 54321170.

Emma: Hello!                  1                     , please?

Jack: Bill? Sorry, he isn't in at the moment.                     2                      ?

Emma: This is Emma.

Jack:                  3                      ?

Emma: Sure, that's very kind of you. Could you please tell him to call me this evening?

Jack: All right.                        4                                 ?

Emma: It's 54318972.

Jack: I'll tell him as soon as he comes back.

Emma:                    5                         .

Jack: You are welcome.