The total mass of nutrient matter that makes up the Earth is ________

Options

A. increasing
B. sometimes increasing and sometimes decreasing
C. constant
D. decreasing

Answer

To answer the question about the total mass of nutrient matter that makes up the Earth, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Main Nutrients**: The primary nutrients that make up the Earth's matter include nitrogen, oxygen, carbon, and hydrogen. These elements are essential for life and are part of various biological and geological cycles.

2. **Understand the Composition**:
- Nitrogen constitutes approximately 71% of the Earth's atmosphere.
- Oxygen makes up about 21%.
- Carbon is present at around 0.3%.
- Hydrogen accounts for roughly 0.75%.

3. **Recognize the Nutrient Cycles**: These nutrients are continuously cycled through various processes in the ecosystem, such as photosynthesis, respiration, and decomposition. This cycling ensures that there is no net loss or gain of these nutrients in the environment.

4. **Conclude on Nutrient Matter**: Given that the nutrient matter is constantly recycled and remains in balance, we can conclude that the total mass of nutrient matter that makes up the Earth is constant.

5. **Select the Correct Option**: Based on the understanding that the nutrient matter remains constant due to the cycles, the correct answer to the question is that the total mass of nutrient matter that makes up the Earth is constant.

### Final Answer:
The total mass of nutrient matter that makes up the Earth is **constant**.

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