A hormone delaying senescence is :

Options

A. Auxin
B. Cytokinin
C. Ethylene
D. Gibberellin

Answer

To answer the question "A hormone delaying senescence is:", we need to identify the hormone that is known for its role in delaying the aging process in plants.

### Step-by-Step Solution:

1. **Understanding Senescence**: Senescence is the process of aging in plants, which leads to the deterioration of plant tissues and ultimately death. It is a natural part of a plant's life cycle.

2. **Identifying Plant Hormones**: There are several hormones in plants that regulate growth, development, and aging. The main hormones include auxins, gibberellins, cytokinins, ethylene, and abscisic acid.

3. **Role of Cytokinins**: Among these hormones, cytokinins are known to delay senescence. They promote cell division and growth, and they help in maintaining the vitality of the plant tissues by delaying the aging process.

4. **Conclusion**: Therefore, the hormone that delays senescence is **cytokinins**.

### Final Answer:
A hormone delaying senescence is **cytokinins**.