What is true about any ecosystem:-

Options

A. It is self regulatory.
B. It is self sustained
C. Top carnivores have climax trophic level position.
D. All

Answer

### Step-by-Step Solution:

1. **Understanding Ecosystem Characteristics**:
- An ecosystem is a community of living organisms interacting with their physical environment. It has certain characteristics that define its nature.

2. **Self-Regulatory Nature**:
- Ecosystems are self-regulatory, meaning they have mechanisms to maintain balance and equilibrium without external control. This includes processes like nutrient cycling and population control.

3. **Self-Sustaining Aspect**:
- Ecosystems are self-sustained, as they can maintain their structure and function over time. They rely on internal processes to provide energy and nutrients, primarily through producers (like plants) that convert sunlight into energy.

4. **Trophic Levels**:
- In an ecosystem, organisms are organized into trophic levels based on their feeding relationships. The primary producers (plants) are at the first level, followed by herbivores (primary consumers) at the second level, then predators (secondary consumers) at the third level, and finally, carnivores (top predators) at the fourth level.

5. **Climax Trophic Level**:
- The term "climax trophic level" refers to the highest level in the food chain, which is occupied by top carnivores. They play a crucial role in regulating the populations of other species within the ecosystem.

6. **Conclusion**:
- All the statements provided in the question about ecosystems are true. Therefore, the correct answer is "all."

### Final Answer:
The true statements about any ecosystem are:
- It is self-regulatory.
- It is self-sustained.
- Top carnivores have a climax trophic level position.
Thus, the correct answer is **"all."**