Phytotron is

Options

A. Fish culture
B. Plant hormone
C. Animal hormone
D. None of these

Explanation

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for the definition of "phyto-tron" and provides four options: fish culture, plant hormone, animal hormone, and none of these.

2. **Identifying the Correct Definition**: A phyto-tron is not related to fish culture, plant hormones, or animal hormones. Instead, it refers to a specific type of laboratory.

3. **Defining Phyto-tron**: A phyto-tron is an enclosed laboratory designed for studying plants and their interactions with the environment. This includes examining how plants respond to various environmental factors, including climate change and greenhouse gases.

4. **Conclusion**: Since none of the provided options accurately describe a phyto-tron, the correct answer is "none of these."

5. **Final Answer**: The correct option is "none of these."