A climacteric fruit is

Options

A. Trapa
B. Apple
C. Almond
D. Pistachio.

Answer

### Step-by-Step Solution:

1. **Understanding Climacteric Fruits**: Climacteric fruits are those that continue to ripen after being harvested. This ripening process is associated with an increase in ethylene production, a natural plant hormone.

2. **Characteristics of Climacteric Fruits**:
- They exhibit a significant increase in cellular respiration during the ripening process.
- They can ripen off the tree, meaning they do not need to remain attached to the plant to mature.

3. **Examples of Climacteric Fruits**: Common examples include banana, apple, mango, melon, and apricot. These fruits are known for their ability to ripen post-harvest due to the ethylene they produce.

4. **Analyzing the Options**: The options given are:
- Trepa
- Apple
- Almond
- Pistachio

5. **Identifying the Correct Answer**: Among the options, apple is a well-known climacteric fruit, as it ripens after being picked and is associated with increased ethylene production.

6. **Final Answer**: Therefore, the answer to the question "A climacteric fruit is" is **apple**.