This paint mixes easily with water.

　You should mix up all the ingredients.

　It's too easy to mix him up with his brother. They look the same.

三、重点语法---祈使句

祈使句指的是表示命令、请求、建议或劝告的句子。其主语you常省略，谓语动词用原形，句末用感叹号或句号，读降调。

1. 肯定的祈使句

（1）动词原形+其他

Stand up, please. = Please stand up.

（2）Be + adj.

Be careful! = Look out! = Take care!

（3）Let's + 动词原形

Let's go to school together.

2. 否定的祈使句

（1） Don't + 动词原形

Don't stand up.

　Don't be careless. 别粗心。

（2）Let's ( let sb ) + not + 动词原形

　Let's not say anything about it. 对于这件事，咱们什么也别说。

　Let them not play with fire. 别让他们玩火。

3. 祈使句的反意疑问句

(1) 肯定祈使句的反意疑问句反问部分用will you 或won't you。

　Please open the door, will/ won't you?

(2) 否定祈使句的反意疑问句反问部分只用will you。

　Don't be late again, will you?

(3) 以let's开头的祈使句反意疑问句反问部分用shall we。

　Let's turn on the TV, shall we?

1. _______ cross the road until the traffic lights turn green.

A. Not B. Won't C. Doesn't D. Don't

2. Please help me carry it, ______?

A. will I B. will you C. shall I D. shall we

3. Kate, _______ your homework here tomorrow.

A. bring B. brings C. to bring D. bringing

4. Don't you know that _______ is good for our health?

A. swim B. swimming C. swam D. swims