Which of the following statements is not true?

Options

A. `CO_(2)` is the best fire extinguisher
B. Global warming can cause acid rain
C. Burning of coal and diesel releases sulphur dioxide `(SO_(2))` gas
D. LPG has higher calorific value than biogas

Answer

To solve the question "Which of the following statements is not true?", we need to evaluate each of the given statements one by one and determine their validity.

### Step-by-Step Solution:

1. **Evaluate Statement 1: "CO2 is the best fire extinguisher."**
- This statement is true. Carbon dioxide (CO2) is effective in extinguishing fires as it displaces oxygen, which is necessary for combustion. By cutting off the oxygen supply, CO2 helps to put out the fire.

2. **Evaluate Statement 2: "Global warming causes AC drain."**
- This statement is false. Global warming is primarily caused by the increase in greenhouse gases like carbon dioxide and CFCs, which leads to a rise in Earth's temperature. AC drain refers to acid rain, which is caused by nitrogen oxides and sulfur oxides mixing with rainwater, not directly by global warming.

3. **Evaluate Statement 3: "Burning of coal and diesel releases sulfur dioxide gas."**
- This statement is true. The combustion of coal and diesel fuels produces sulfur dioxide (SO2), which is a colorless gas with a strong choking odor. This is a well-known fact in environmental science.

4. **Evaluate Statement 4: "LPG has a higher calorific value than biogas."**
- This statement is true. The calorific value of LPG is approximately 55,000 kJ/kg, while biogas has a calorific value ranging from 35,000 to 40,000 kJ/kg. Therefore, LPG does indeed have a higher calorific value than biogas.

### Conclusion:
After evaluating all the statements, we find that the statement that is not true is **Statement 2: "Global warming causes AC drain."** Therefore, the answer to the question is **Option 2**.

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