Hormone primarily concern with cell division is

Options

A. IA A
B. NA A
C. cytokinin
D. gibberellic acid

Answer

### Step-by-Step Solution:

1. **Identify the Hormones**: The question asks for the hormone primarily concerned with cell division. The options given are IAA (Indole-3-acetic acid), NAA (Naphthaleneacetic acid), Cytokinin, and Gibberellin.

2. **Understand the Function of Cytokinin**: Cytokinins are plant hormones that play a crucial role in promoting cell division (cytokinesis) in plant cells. The term "cytokinin" itself is derived from "cyto," meaning cell, and "kinin," meaning to divide.

3. **Role of Auxin**: Cytokinins work in conjunction with another hormone called auxin. Auxin is primarily responsible for cell elongation and growth, and it is found at the tips of the plant. The balance between auxin and cytokinin levels influences whether the plant will grow roots or shoots.

4. **Cytokinin to Auxin Ratio**: The ratio of cytokinin to auxin is important in determining the type of growth. A higher concentration of cytokinin relative to auxin promotes stem growth, while a higher concentration of auxin relative to cytokinin promotes root growth.

5. **Conclusion**: Based on the information gathered, the hormone primarily concerned with cell division is **Cytokinin**.

### Final Answer:
The hormone primarily concerned with cell division is **Cytokinin**.

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