Assertion: The concentration of pollutants in water or atmosphere is often expressed in terms of ppm
Reason :Concentration in parts per million can be expressed as mass to mass, volume of volume and mass to volume .

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion
B. If both assertion and reason are true but reason is not the correct explanation of assertion.
C. If assertion is true but reason is false
D. If both assertion and reason are false

Explanation

To solve the question, we need to analyze both the assertion and the reason provided.

### Step 1: Understand the Assertion
The assertion states that "The concentration of pollutants in water or atmosphere is often expressed in terms of ppm."
- **Explanation**: PPM stands for "parts per million," which is a unit used to measure very dilute concentrations of substances. In environmental science, it is common to express the concentration of pollutants in water or air in ppm because these pollutants are often present in very low concentrations.

### Step 2: Understand the Reason
The reason states that "Concentration in parts per million can be expressed as mass to mass, volume to volume, and mass to volume."
- **Explanation**: This statement is accurate. PPM can indeed be calculated in different ways depending on the context:
- Mass to mass (e.g., mg of pollutant per kg of solution)
- Volume to volume (e.g., mL of pollutant per L of solution)
- Mass to volume (e.g., mg of pollutant per L of solution)

### Step 3: Analyze the Relationship between Assertion and Reason
Now, we need to determine if the reason provided is a correct explanation for the assertion.
- While both the assertion and reason are true, the reason does not directly explain why ppm is used for pollutants. The assertion focuses on the common practice of using ppm for low concentrations, while the reason describes how ppm can be expressed.

### Conclusion
Based on the analysis:
- The assertion is true.
- The reason is true but does not serve as a correct explanation for the assertion.

### Final Answer
The correct option is that both the assertion and reason are true, but the reason is not the correct explanation for the assertion.

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