Which among the following is a major water pollutant leading to the death of aquatic species?

Options

A. Pesticides and fertilisers
B. River water dumped into sea
C. Chlorine
D. Untreated domestic sewage

Answer

To solve the question regarding which is a major water pollutant leading to the death of aquatic species, we can analyze the options provided step by step.

### Step 1: Understand the Question
The question asks for a major water pollutant that causes the death of aquatic species. This means we need to identify substances that, when introduced into water bodies, can harm aquatic life.

### Step 2: Analyze the Options
1. **Pesticides and Fertilizers**: These are chemicals used in agriculture to enhance crop production and control pests. When they run off into water bodies, they can be toxic to aquatic life, leading to their death.

2. **River Water Dumped into the Sea**: This option suggests that river water, when dumped into the sea, does not cause harm. This is incorrect because river water itself is not a pollutant; it is a natural source of water.

3. **Chlorine**: Chlorine is often used to disinfect water. While it can be harmful in high concentrations, it is generally used to treat water and does not lead to widespread death of aquatic species.

4. **Untreated Domestic Sewage**: This can indeed be harmful to aquatic life, but the question asks for a major pollutant. While untreated sewage can cause problems, it may not be as significant as pesticides and fertilizers in terms of widespread impact.

### Step 3: Identify the Correct Answer
After evaluating all options, **pesticides and fertilizers** emerge as the major water pollutant that leads to the death of aquatic species. They are specifically designed to kill pests, and when they enter water bodies, they can have lethal effects on fish and other aquatic organisms.

### Conclusion
The correct answer to the question is **pesticides and fertilizers**.

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