火炬信号点燃后能发出强烈的红色火光，是要求列车紧急停车的一种视觉信号。（）

The man _____his coat as soon as he walked into the warm room.[ ]

A. took away

B. took down

C. took off

D. took on

句型转换。

1. Remember we're going to the theatre tonight. (同义句)

    _____ _____ we're going to the theatre tonight.

2. Please go and get my glasses for me from the drawer. (同义句)

    Please _____ _____ my glasses from the drawer.

3. They're going to buy a house when they've saved enough money. (同义句 )

    They _____ _____ _____ a house when they've saved enough money.

4. What's for dinner tonight? (同义句)

    What's _____ _____ _____ tonight?

5. Let's cheer her up,  _____ _____? (反意疑问句)

物体b在水平推力F作用下，将物体a挤压在竖直墙壁上，如图所示，a、b 处于静止状态，关于a、b两物体的受力情况，下列说法正确的是 

A．a受到两个摩擦力的作用

B．a共受到四个力的作用

C．b共受到三个力的作用

D．a受到墙壁摩擦力的大小不随F的增大而增大

螺纹的主要参数有哪些

一条线路长度如不超过20公里，一般设置（）个车辆段。

A.1

B.2

C.3

D.4