Task 1: 

1. mustn't

2. must

3. mustn't

4. must

5. must

Task 2:

1. B

2.A

3. A

4.B

5.A

Task 3:

... must comply with the general school rules, for example wearing a uniform when going to school, strictly prohibiting smoking in school, etc.

Task 4:

1. more intelligent 

2. older

3. larger

4. more colourful

5. qiueter

6. more boring

7.bigger

8.worse

9.more beautiful

10.better

Task 5:

2. No desert in the world is hotter than Sahara

3. My mother is the busiest person in my family.

5. I have never seen worse film than this film

1: 

1. mustn't

2. must

3. mustn't

4. must

5. must

2:

1. B

2.A

3. A

4.B

5.A

 4:

1. more intelligent 

2. older

3. larger

4. more colourful

5. qiueter

6. more boring

7.bigger

8.worse

9.more beautiful

10.better