1. The correct answer is D. "if" because it introduces a conditional relationship between eating less fast food and being healthier.
2. The correct answer is D. "because" because it explains the reason for eating more red vegetables and fruit.
3. The correct answer is B. "when" because it indicates the appropriate time to use eyedrops.
4. The correct answer is C. "or" because it presents a choice between eating spinach or cabbage.
5. The correct answer is C. "but" because it contrasts reading in dim light with the consequence of ruining eyesight.
6. The correct answer is C. "and" because it shows a positive relationship between laughter and love being good for health.
7. The correct answer is A. "because" because it provides a reason why young people want to avoid acne.
8. The correct answer is B. "and" because it shows that the brother likes both running and cycling.
9. The correct answer is B. "and" because it suggests standing up every hour and doing some simple exercise to reduce sitting time.
10. The correct answer is B. "or" because it presents a choice between eating a lot of meat or snacks