Which of the following is/are elastic gel?

Options

A. Gelatin
B. Silicic acid
C. Agar agar
D. Starch

Explanation

To determine which of the given options are elastic gels, we need to analyze each substance based on the definition of a gel and the characteristics of elastic gels.

### Step-by-Step Solution:

1. **Understanding Gels**:
- A gel is a colloidal system where the dispersed phase is liquid and the dispersion medium is solid.
- Elastic gels can change shape when a force is applied and return to their original shape once the force is removed.

2. **Analyzing Each Option**:
- **Option 1: Gelatin**
- Gelatin is a protein derived from collagen and forms a gel-like structure when mixed with water. It exhibits elasticity, allowing it to return to its original shape after deformation.
- **Conclusion**: Gelatin is an elastic gel.

- **Option 2: Salicylic Acid**
- Salicylic acid is an organic compound and does not form a gel structure. It is primarily used in pharmaceuticals and does not exhibit the characteristics of an elastic gel.
- **Conclusion**: Salicylic acid is not an elastic gel.

- **Option 3: Agar-Agar**
- Agar-agar is a gelatinous substance derived from algae. It forms a gel when dissolved in hot water and solidifies upon cooling. Agar-agar also shows elastic properties, making it capable of returning to its original shape.
- **Conclusion**: Agar-agar is an elastic gel.

- **Option 4: Starch**
- Starch can form a gel-like structure when mixed with water and heated. It can exhibit elasticity, especially in the form of a gel when prepared correctly.
- **Conclusion**: Starch is an elastic gel.

3. **Final Answer**:
- The substances that are elastic gels from the options provided are:
- Option 1: Gelatin
- Option 3: Agar-Agar
- Option 4: Starch

### Summary of Correct Options:
- **Elastic Gels**: Gelatin, Agar-Agar, Starch
- **Not an Elastic Gel**: Salicylic Acid