Turnip mosaic disease is caused by

Options

A. bacteria
B. viruses
C. nematodes
D. fungi

Explanation

**Step-by-Step Solution:**

1. **Identify the Disease**: The question asks about "turnip mosaic disease," which is a specific disease affecting plants, particularly cruciferous plants.

2. **Determine the Causative Agent**: To answer the question, we need to identify what causes turnip mosaic disease. The options provided are bacteria, viruses, nematodes, and fungi.

3. **Research the Disease**: Turnip mosaic disease is known to affect plants in the Brassicaceae family (cruciferous plants).

4. **Identify the Correct Pathogen**: Upon research, it is established that turnip mosaic disease is caused by a virus known as the Turnip Mosaic Virus (TUMV).

5. **Classify the Virus**: The Turnip Mosaic Virus belongs to the family Potiviridae, which is a family of plant viruses.

6. **Select the Correct Answer**: Based on the information gathered, the correct answer to the question "Turnip mosaic disease is caused by" is viruses.

7. **Final Answer**: Therefore, the answer is option B: viruses.

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