Name two food materials which can be preserved by using oil or vinegar.

Explanation

**Step-by-Step Solution:**

1. **Understanding Preservation**: Oil and vinegar are natural preservatives that help in extending the shelf life of food by preventing microbial growth.

2. **Identifying Food Materials**: We need to name two food materials that can be preserved using oil or vinegar.

3. **Examples of Food Materials**:
- **Pickles**: These are commonly preserved using oil or vinegar. The acidic environment created by vinegar or the sealing effect of oil helps in preventing spoilage.
...