Here are the answers for each sentence:

1. **Don't touch your face with** **dirty** **hands.**
- **D. clean**

2. **Breakfast is very** **important**, **so you shouldn’t skip it.**
- **A. trivial**

3. **Remember to** **wear** **a hat and use some sunscreen when you go to the beach.**
- **D. take off**

4. **If you don’t want to** **gain** **weight, you should go to the gym every day.**
- **C. lose**

5. **Clean hands help** **prevent** **the spread of some diseases.**
- **B. stop**

These selections reflect the opposite meanings as requested.