在一次水灾中，大约有2.5×10⁵个人无家可归，假如一顶帐篷占地100米²，可以放置40个床位，为了安置所有无家可归的人，需要多少顶帐篷？这些帐篷大约要占多少地方？估计你的学校的操场可安置多少人？要安置这些人，大约需要多少个这样的操场？

— I like this dress, Mum.

下列四幅地图中，内容最详细的是（    ）　　

补全对话。每空一词。

Dave: Hi, Mona! I am going to have a birthday ____. I want to have it on Saturday evening. Can you come?

Mona: Oh, I am going to  ____ my grandfather on Saturday evening.

Dave: What about Sunday?

Mona: I have to take the piano lessons.

Dave: Oh! When are you ____ then?

Mona: Well, Friday is fine.

Dave: Friday? That’s tomorrow! OK. We can have it then. Can you ask Ali to ____    us?

Mona: Sure. When and where shall we meet?

Dave: Near our school gate at half ____ four.

Mona: Great! See you then!

Dave: Bye!

如图所示是显微镜视野中某细胞的一部分模式图．下列有关叙述正确的是（　　）