2
Below is a question with multiple-choice answers. Choose the correct option based on your reasoning.

### Question:
Scurvy is a disease that sailors often got on long voyages. It was discovered that scurvy could be prevented by eating oranges and lemons. This suggests that scurvy is a disease caused by

### Choices:
1. exposure to sea air
2. a nutritional deficiency
3. a microorganism
4. lack of exercise

### Answer:
