Read the following passage
Human body is made up of five important components, of which water is the main component. Food as well as potable water is essential for every human being. The food is obtained from plants through agriculture, Pesticides are being used extensively for a high yield in the fields. These pesticides are absorbed by the plants from the soil along with water and minerals and from the water bodies these pesticides are taken up by the aquatic animals and plants. As these chemicals are not biodegradable, they get accumulated progressively at each trophic level. The maximum concentration of these chemicals gets accumulated in our bodies and greatly affects the health of our mind and body.
First link in any food chain is usually green plants. Which of the following statements gives the correct explanation about the above statement?

Options

A. Only green plants have the capacity to synthesize food using sunlight.
B. There are more herbivores than carnivores in a food chain.
C. Green plants are the only ones fixed at one place in the soil and do not show any kind of movements.
D. Green plants are widely distributed.

Explanation

To answer the question regarding the statement "First link in any food chain is usually green plants," we need to analyze the provided options one by one to find the correct explanation.

### Step-by-Step Solution:

1. **Understanding the Statement**: The statement indicates that green plants are the primary producers in a food chain. This means they are the first link because they can produce their own food through photosynthesis.

2. **Evaluating Each Option**:
- **Option A**: "Green plants have the capacity to synthesize food using sunlight."
- This statement is true. Green plants perform photosynthesis, which allows them to convert sunlight into energy and produce food. This ability is a key reason why they are the first link in the food chain.

- **Option B**: "There are more herbivores than carnivores in a food chain."
- While this statement is generally true, it does not explain why green plants are the first link. It merely describes a characteristic of food chains and does not relate to the role of green plants.

- **Option C**: "Green plants are the only ones fixed at one place in the soil and do not show any kind of movements."
- Although green plants are indeed stationary, this characteristic alone does not justify their position as the first link in the food chain. Other organisms, like fungi, are also stationary but do not perform photosynthesis.

- **Option D**: "Green plants are widely distributed."
- While it is correct that green plants can be found in various environments, being widely distributed does not explain why they are the first link in the food chain. Other organisms are also widely distributed.

3. **Conclusion**: After analyzing all options, **Option A** is the only statement that correctly explains why green plants are the first link in the food chain due to their ability to synthesize food using sunlight.

### Final Answer:
**The correct explanation for the statement is Option A: "Green plants have the capacity to synthesize food using sunlight."**