A: Productivity of eutrophic lake is maximum.
R: Eutrophication is mainly due to addition of `SO_(4^(2-))` and heavy metals.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion, then mark (1).
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark (2)
C. If Assertion is true statement but Reason is false, then mark (3)
D. If both Assertion and Reason are false statements, then mark (4).

Answer

To solve the question, we need to analyze the assertion (A) and the reason (R) provided:

**Assertion (A):** Productivity of eutrophic lake is maximum.

**Reason (R):** Eutrophication is mainly due to addition of \( SO_4^{2-} \) and heavy metals.

### Step-by-Step Solution:

1. **Understanding Eutrophic Lakes:**
- Eutrophic lakes are characterized by high biological productivity. This is primarily due to the presence of high levels of nutrients, particularly nitrogen and phosphorus, which promote the growth of algae and aquatic plants.

2. **Evaluating the Assertion (A):**
- The assertion states that the productivity of eutrophic lakes is maximum. This is true because eutrophic lakes have abundant nutrients that support a large biomass of aquatic life. Therefore, the assertion is correct.

3. **Evaluating the Reason (R):**
- The reason states that eutrophication is mainly due to the addition of \( SO_4^{2-} \) (sulfate ions) and heavy metals. This is incorrect because eutrophication is primarily caused by the addition of nitrogen and phosphorus, not sulfate ions or heavy metals. While heavy metals can be pollutants, they do not contribute to the nutrient enrichment that leads to eutrophication.

4. **Conclusion:**
- Since the assertion is true and the reason is false, we can conclude that the correct relationship is that the assertion is true, but the reason is false.

### Final Answer:
The correct option is that the assertion is true but the reason is false.

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