If at high altitudes, birds become rare, the plants likely to disappear are

Options

A. Pine
B. Orchids
C. Oak
D. Rhododendrons.

Answer

### Step-by-Step Solution:

1. **Understand the Question**: The question asks which plants are likely to disappear if birds become rare at high altitudes. This implies a relationship between birds and certain plants, particularly in terms of pollination.

2. **Analyze the Options**: We have four options to consider:
- **A. Pine**: Pine trees are gymnosperms that do not rely on birds for pollination; they are wind-pollinated.
- **B. Orchids**: Orchids are typically found at lower altitudes and are pollinated by insects, not birds.
- **C. Oak**: Oak trees are also found in temperate regions and are not specifically associated with high altitudes or bird pollination.
- **D. Rhododendrons**: These are flowering plants found in mountainous regions and are known to be pollinated by birds.

3. **Evaluate Each Option**:
- **Pine**: Since they are wind-pollinated, they are not dependent on birds, making them an unlikely candidate for disappearance due to rare birds.
- **Orchids**: As they are primarily pollinated by insects and found at lower altitudes, they are not affected by the rarity of birds at high altitudes.
- **Oak**: Similar to pine, oaks do not rely on birds for pollination and are not specifically linked to high altitudes.
- **Rhododendrons**: These plants are specifically adapted to mountainous regions and rely on birds for pollination. If birds become rare, rhododendrons are likely to face extinction.

4. **Select the Correct Answer**: Based on the analysis, the correct answer is **D. Rhododendrons**. They are the plants most likely to disappear if birds become rare at high altitudes due to their reliance on birds for pollination.

### Final Answer:
The plants likely to disappear if birds become rare at high altitudes are **Rhododendrons (Option D)**.

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