A long-short day plant is

Options

A. Bryophyllum
B. Tomato
C. Potato
D. Cucumber.

Answer

### Step-by-Step Solution:

1. **Understanding Plant Categories**:
- Plants can be classified based on their light requirements for flowering into three main categories: short-day plants, long-day plants, and day-neutral plants.
- Short-day plants require longer periods of darkness and shorter periods of light to flower.
- Long-day plants require shorter periods of darkness and longer periods of light to flower.

2. **Identifying the Characteristics of Each Plant**:
- **Bryophyllum**: This plant is known to be a long-short day plant, meaning it requires a specific combination of short and long days to initiate flowering.
- **Tomato**: This is classified as a day-neutral plant, which means it can flower regardless of the length of day or night.
- **Potato**: This is categorized as a long-day plant, which means it requires longer daylight hours to flower.
- **Cucumber**: Similar to tomato, cucumber is also a day-neutral plant.

3. **Determining the Correct Answer**:
- Since the question asks for a long-short day plant, we need to identify which of the given options fits this description.
- Among the options provided, **Bryophyllum** is the only plant that requires both short and long days for flowering, making it the correct answer.

### Final Answer:
The long-short day plant among the options is **Bryophyllum**.

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