Which of the following is correct match?

Options

A. Photochemical smog : `SO_(2)`
B. Nitrate in drinking water : Blue baby syndrome
C. Phosphate fertilisers in water : BOD level of water increase
D. All are correct

Answer

To determine which of the options provided in the question is a correct match, we will analyze each option one by one.

### Step 1: Analyze Option 1 - Photochemical Smog and SO2
- Photochemical smog is a type of air pollution that occurs when sunlight reacts with pollutants such as nitrogen oxides and volatile organic compounds.
- Sulfur dioxide (SO2) is a significant contributor to air pollution but is not directly responsible for photochemical smog. Instead, it contributes to acid rain.
- Therefore, **Option 1 is incorrect**.

### Step 2: Analyze Option 2 - Nitrate in Drinking Water and Blue Baby Syndrome
- Blue baby syndrome is caused by methemoglobinemia, which occurs when infants consume water with high levels of nitrates.
- Nitrates convert hemoglobin into methemoglobin, which cannot carry oxygen effectively, leading to a lack of oxygen in the body.
- Thus, **Option 2 is correct**.

### Step 3: Analyze Option 3 - Phosphate Fertilizer in Water and BOD Level
- Biological Oxygen Demand (BOD) measures the amount of oxygen required by microorganisms to decompose organic matter in water.
- When phosphate fertilizers enter water bodies, they promote algal blooms. The decomposition of this algae consumes oxygen, leading to a decrease in dissolved oxygen levels.
- Therefore, **Option 3 is correct**.

### Step 4: Analyze Option 4 - ALAR
- ALAR (Alar) is a chemical that was used as a plant growth regulator. Concerns about its safety led to its ban in many countries.
- However, the option does not provide a clear match with any environmental issue or health effect.
- Therefore, **Option 4 is not clearly correct**.

### Conclusion
From the analysis:
- **Option 1 is incorrect**.
- **Option 2 is correct**.
- **Option 3 is correct**.
- **Option 4 is not clearly correct**.

Thus, the correct matches are Options 2 and 3.

### Final Answer
The correct matches are:
- Option 2: Nitrate in drinking water causes blue baby syndrome.
- Option 3: Phosphate fertilizer in water increases BOD levels.

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