The cabbage becomes brown due to the deficiency of …………………………………

Explanation

**Step-by-Step Solution:**

1. **Identify the Plant:** The question specifically mentions "cabbage." It is important to focus on the specific plant in question to understand its nutrient requirements.

2. **Understand Nutrient Deficiency Symptoms:** Different plants exhibit different symptoms when they lack essential nutrients. In the case of cabbage, we need to determine which nutrients are critical for its health.

3. **Research Nutrient Deficiencies:** Cabbage, like many other plants, can show specific symptoms when it is deficient in certain nutrients. Common symptoms include discoloration, wilting, and stunted growth.

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