The long-day plant is

Options

A. Tomato
B. Potato
C. Cotton
D. Spinach.

Answer

**Step-by-Step Solution:**

1. **Understanding Long-Day Plants**: Long-day plants are those that require longer daylight hours to initiate flowering. They typically flower when the day length exceeds a certain critical threshold.

2. **Identifying Characteristics**: These plants generally need a longer duration of light and a shorter duration of darkness. They usually bloom in the summer months when the days are longer.

3. **Analyzing the Options**:
- **Tomato**: This is classified as a day-neutral plant, meaning it does not depend on the length of day or night to flower.
- **Potato**: Potatoes are known to be long-day plants, as they require longer daylight to flower.
- **Cotton**: Cotton is a short-day plant, which means it flowers when the day length is shorter than its critical length.
- **Spinach**: Spinach is also a long-day plant, requiring extended daylight for flowering.

4. **Conclusion**: Based on the characteristics and classifications, the correct answers for long-day plants from the options provided are **Potato** and **Spinach**.

**Final Answer**: The long-day plants are **Potato** and **Spinach**.

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