Which creature can maintain the fertility of soil ?

Options

A. Bacteria
B. Fungi
C. Rat
D. Earthworm

Explanation

**Step-by-Step Solution:**

1. **Understanding Soil Fertility**: Soil fertility refers to the ability of soil to provide essential nutrients to plants, which is crucial for their growth and development. Fertile soil supports healthy crop yields.

2. **Identifying Soil Creatures**: The question asks about creatures that can maintain soil fertility. We have four options: bacteria, fungi, wheat, and earthworm.

3. **Analyzing Each Option**:
- **Bacteria**: While bacteria play a role in nutrient cycling and decomposition, they are not the primary creatures associated with maintaining soil structure and fertility.
- **Fungi**: Fungi also contribute to nutrient cycling and can form symbiotic relationships with plants, but they do not physically aerate the soil or improve its structure in the same way as some other organisms.
- **Wheat**: Wheat is a plant and does not maintain soil fertility; rather, it relies on the fertility of the soil to grow.
- **Earthworm**: Earthworms are known as "friends of the soil" because they burrow through the soil, which aerates it and improves its structure. They also break down organic matter, enriching the soil with nutrients.

4. **Conclusion**: After analyzing all options, the creature that can maintain the fertility of soil is the earthworm.

5. **Final Answer**: The correct answer is D - Earthworm.

---