根据对话内容，从对话后的选项中选出能填入空白处的最佳选项。选项中有两项为多余选项。

一Good afternoon，Miss May．

一Good afternoon，Parker． 小题1:   .

一Because we’ve just finished our swimming class．

一 小题2:

一That’s the teaching plan．Can you swim，Miss May?

一小题3: .

—Are you fond of it?

一 小题4:  .

一So you are a good swimmer．

一Oh，no.  小题5: .I learn it every year but I can’t learn it well．

A．Yes，I like it very much．

B．I don’t think it a good idea to have swimming class at noon．

C．I’m a very poor swimmer．

D．Why do all of you look so tired? E．Only a little．

F．oh，yes, that’s quite easy．

G．You should have a good rest，then．

下图是公元纪年年代尺。郑和下西洋应在哪一段？[ ]