悬停在空中的直升机受到升力和____ 力的作用，其中升力的施力物体是　____ 　．如图所示，父子俩相持不下，此现象表明力的作用效果与力的大小、方向和　____ 　有关．

绦虫和蛔虫均为肠道寄生虫，蝗虫对禾本科作物危害很大．青蛙被称为“田园卫士”．绦虫、蛔虫、蝗虫、青蛙它们分别属于（　　）

选词填空，将序号写在横线上即可。

A: Excuse me. Can you help me?

B: Of course.  ____ can I help you?

A.I am looking for a____

B:____ size do you wear?

A: Medium, I think.

B: Here. How do you like this one?

A: It's ____. Can I try it on?

B: You can try it on in the ____ over there.