A thick fleshy underground horizontal main stem is

Options

A. corm
B. tuber
C. sucker
D. rhizome

Answer

To answer the question "A thick fleshy underground horizontal main stem is," we need to analyze the options provided: comb, tuber, sucker, and rhizome.

### Step-by-Step Solution:

1. **Understanding the Options**:
- **Comb**: This is a vertical fleshy underground stem that acts as a food storage organ in certain seed plants. Since it is vertical, it does not fit the description of a horizontal stem.
- **Tuber**: Tubers are enlarged parts of the plant that serve as storage containers. They can be root tubers or stem tubers, but they do not grow horizontally underground. Therefore, this option is also incorrect.
- **Sucker**: A sucker refers to a lateral shoot that develops from a rhizome. It emerges from the soil near the parent plant and is involved in asexual reproduction. However, it does not describe a thick fleshy underground horizontal stem, making this option incorrect as well.
- **Rhizome**: Rhizomes are continuously growing horizontal underground stems. They can produce lateral shoots and adventitious roots at regular intervals. This matches the description of a thick fleshy underground horizontal main stem.

2. **Conclusion**: Based on the analysis of each option, the correct answer is **rhizome**.

### Final Answer:
A thick fleshy underground horizontal main stem is called a **rhizome**.