A gradual increase in the average temperature of earth's atmosphere is known as:

Options

A. acid rain
B. global warming
C. deforestation
D. None of the above

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the term that describes the gradual increase in the average temperature of Earth's atmosphere.

2. **Analyzing the Options**:
- **Option 1: Acid Rain**: This refers to rain that has become acidic due to pollutants in the atmosphere. It does not relate to the increase in temperature.
- **Option 2: Global Warming**: This term refers specifically to the rise in Earth's average temperature due to increased concentrations of greenhouse gases in the atmosphere.
- **Option 3: Deforestation**: While deforestation can contribute to climate change, it is not the term that describes the increase in temperature itself.

3. **Identifying the Correct Answer**: After analyzing the options, it is clear that the correct term for the gradual increase in Earth's average temperature is "Global Warming".

4. **Final Answer**: The answer to the question is **Global Warming**.

---