Assertion : Agar is used to grow microbes and in preparation of ice-creams and jellies
Reason : Agar is a hydrocolloid which is produced by certain marine brown algae.

Options

A. If both assertion and reason are true and the reason is the correct explanation of the assertion
B. If both assertion and reason are true and but reason is not the correct explanation of the assertion
C. If assertion is true but reason is false
D. If both assertion and reason are false

Explanation

To solve the question regarding the assertion and reason about agar, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Assertion**: The assertion states that "Agar is used to grow microbes and in the preparation of ice creams and jellies."
- **Analysis**: This is true. Agar is indeed used as a culture medium for growing microbes in laboratories and is also a common ingredient in food products like ice creams and jellies due to its gelling properties.

2. **Understand the Reason**: The reason states that "Agar is a hydrocolloid which is produced by certain marine brown algae."
- **Analysis**: This statement is partially true. Agar is classified as a hydrocolloid because it can hold water and form gels. However, it is primarily obtained from red algae (specifically from genera like Gelidium and Gracilaria), not brown algae. Therefore, while agar is a hydrocolloid, the assertion about its source is incorrect.

3. **Evaluate the Relationship**: Now, we need to determine if both the assertion and reason are true or false.
- The assertion is true, while the reason is false because it incorrectly identifies the source of agar.

4. **Conclusion**: Based on the evaluations:
- The correct option is that the assertion is true and the reason is false.

### Final Answer:
The correct conclusion is that the assertion is true and the reason is false.