在“调查公园的生物”活动中，你认为哪位同学的做法是正确的（　　）

补全对话。

A. I prefer to live on a low floor.

B. What a high floor!

C. Where do you live?    

D. How many floors are there in your flat?

E. Which floor do you live on?

F. I also like to live high.

G. It's convenient to climb up the stairs if there is not a lift to take.

George: I heard you moved to a new flat to live in. ____ 

Millie: I live on the twenty-second floor.

George:____

Millie: Yes. I like living high because I can enjoy a good view.

George:____

Millie:____

George: Seven.I live on the third floor.

Millie:____

如图所示，质量为m的木块P在质量为M的长木板ab上滑行，长木板在水平地面上恰好处于静止状态。若ab与地面间的动摩擦因数为μ₁，木块P与长木板ab间的动摩擦因数为μ₂，设物体受到的最大静摩擦力等于滑动摩擦力，则长木板ab受到地面的摩擦力（     ）