1. Working in book design (can, must, could) mean several things
.2. It (may, might, could) be creating elaborate book covers and jacket designs.
3. It (may, can, have to) mean hours of detailed-oriented layoutwork.
4. This work (may, can, should) be done as a freelancer.
5. Book design and layout (could, can, might) call for all types of graphic design software.
6. Book designers (must, can, may) pay close attention to the legal issues to protect their work.
7. Designers (must, should, can) also look to get their credit on books they design.
8. You (can, should, may) be able to listen to music.
9. That (must, might, can) be a good thing and a bad thing.
10. Designers (can, could, had to) create impressive caricatures of any individuals or characters you require

The choice of profession - is important. It's your future work, daily work. And what it will be depends on what you select your correct path or not. I want to become a lawyer. I do not know How will my fate - if I can join the legal academy ... but I will seek. I want an jurisprudence, learn and know the laws, explain them and help people. That is my goal - to be an educated man, to have a prestigious and valuable work. Of course - and normal salary, which would be enough for life: today it is particularly acute to graduates.

должен сделать

1. I have to do warm-up twice a day because I want to win my competition. 

    Я должен делать разминку дважды в день потому, что я хочу выиграть свое соревнование.

2. I have to help my mother on the weekends because she needs my help  and I can't hurt her. 

    Я должен своей маме потому, что на выходных она нуждается в моей и я не могу ее обидеть.

3. I have to learn all my verse because I need to get a good mark.

    Я должен выучить все свои стихи потому, что мне нужно получить хорошую оценку.

4.  I have to listen my favorite song because it helps me to be in a good mood.

    Я должен послушать мою любимую песню потому, что это мне быть в хорошем настроении. 

5  I have a good student, because it will help me in the future.

 я должна хорошо учится, потому что это мне в будущем.

не должен

1)We should not pollute the nature.

Мы не должны загрязнять природу.

2) I should not eat after seven, because it does harm to my health.

я недолжна кушать после семи, потому что это вредит моему здоровью.

3)  I don't have to come to the first lesson, because I don't have it.

Я не должна приходить на первый урок, потому что у меня его нет.