Explanation:

Opaque, transparent, and translucent:
- Opaque materials do not allow light to pass through them. Light gets absorbed or reflected by these materials. For example, wood, metal, and brick are opaque materials.
- Transparent materials allow light to pass through them easily. They have a clear and unobstructed view. Examples of transparent materials include glass, air, and water.
- Translucent materials allow some light to pass through them, but they scatter and diffuse it. As a result, objects on the other side are not clearly visible. Examples of translucent materials include frosted glass, wax paper, and certain plastics.

Vacuum:
- A vacuum is a space devoid of matter, including air and other particles. It is empty and does not contain any material.
- Since there is no matter present in a vacuum, it does not fall under any of the categories of opaque, transparent, or translucent materials.
- Light cannot pass through a vacuum because there are no particles to interact with and transmit the light. Therefore, a vacuum is neither opaque, transparent, nor translucent.

Correct answer:
- The correct answer is option 'B' - Vacuum is a transparent medium.
- This answer might be confusing because a vacuum is an empty space, and we typically associate transparency with materials like glass or air. However, in the context of the given options, transparent is the most appropriate description for a vacuum.
- It is important to note that a vacuum is not a material in the conventional sense, but rather an absence of matter. Therefore, it does not fit into the categories of opaque or translucent either.

Conclusion:
- In summary, a vacuum is not an opaque, translucent, or heterogeneous medium. It is an empty space devoid of matter and does not fall under any of these categories.