Agar is used `:`

Options

A. to grow microbes
B. as food supplements by space travellers.
C. as drugs
D. in preparations of ice-creams and rubber

Answer

**Step-by-Step Solution:**

1. **Understanding Agar**: Agar is a gelatin-like substance that is derived from red algae, specifically from species such as Gracilaria and Gelidium. It is commonly used in various biological and culinary applications.

2. **Analyzing the Uses of Agar**:
- **Growing Microbes**: One of the primary uses of agar is in microbiology, where it serves as a solid medium for the growth of bacteria and other microorganisms. This is done by preparing agar gel plates that provide the necessary nutrients for microbial growth.
- **Food Supplements**: While agar has many uses in food, it is not specifically used as a food supplement for space travelers; other algae, which are rich in protein, are more commonly used for that purpose.
- **Medicinal Uses**: Agar is not used as a drug itself but can be a component in some pharmaceutical preparations. However, it is not classified as a drug.
- **Food Products**: Agar is indeed used in the preparation of various food items, such as ice creams and jellies, due to its gelling properties. However, it is not used in the preparation of rubber.

3. **Conclusion**: The correct statement regarding the use of agar is that it is used to grow microbes. The other statements regarding its use as a food supplement for space travelers, as drugs, and in the preparation of rubber are incorrect.

**Final Answer**: Agar is used to grow microbes.

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