一定要

• must
• never fail do
• make a point of doing sth.

例句

1. 你要是到伦敦来，一定要到我们这里住住。
   If you ever visit London, you must come and stay with us.
2. 你一定要维护自己的权利。
   You must stand up for your rights.
3. 我一定要就那个问题和你辩论。
   I must take you up on that point.
4. 要做个好推销员一定要有闯劲才能成功。
   A good salesman must be aggressive if he wants to succeed.
5. 父母对孩子一定要严格。
   Parents must be firm with their children.
6. 你一定要和我们一起吃午饭。
   You must join us for lunch.
7. 我一定要把头发理一理了。
   I must have my hair trimmed.
8. 公司一定要在市场中有竞争力。
   Companies must be able to compete in the marketplace.