One of the following is an untrue statement

Options

A. `Ca^(++)` is required by plants for cell division
B. `K^(+)` never enters into structural composition of any compound in plants
C. Copper is an activator for alcohol dehydrogenase
D. Manganese toxicity in plants inhibit calcium translocation in shoot apex

Answer

To determine which statement is untrue regarding mineral nutrition in plants, we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Identify the Statements**: We have several options to evaluate. Let's denote them as:
- Option A: Cvv++ is required by plants for cell division.
- Option B: K+ never enters into the structural composition of any component in plants.
- Option C: Copper is an activator for alcohol dehydrogenase.
- Option D: Manganese toxicity in plants inhibits calcium translocation in sugar.

2. **Evaluate Option A**:
- Cvv++ (Calcium ions) are indeed essential for cell division in plants. This statement is **true**.

3. **Evaluate Option B**:
- Potassium (K+) does not enter into the structural composition of plant components but is crucial for various physiological processes. This statement is also **true**.

4. **Evaluate Option C**:
- The statement claims that copper is an activator for alcohol dehydrogenase. However, this is incorrect; zinc is the actual activator for this enzyme. Therefore, this statement is **false**.

5. **Evaluate Option D**:
- Manganese toxicity can indeed inhibit calcium translocation in plants, which makes this statement **true**.

6. **Conclusion**:
- After evaluating all the options, we find that Option C is the untrue statement, as it incorrectly identifies copper as an activator for alcohol dehydrogenase instead of zinc.

### Final Answer:
The untrue statement is **Option C: Copper is an activator for alcohol dehydrogenase**.

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