Nectar guides become 'visible' to bees because they are

Options

A. Colourless areas which absorb ultraviolet radiations
B. Coloured spots which reflect ultraviolet rays
C. Colourless spots which neither absorb nor reflect ultra-voilet rays
D. Coloured spots which neither absorb nor reflect ultra-violet rays.

Answer

To answer the question "Nectar guides become 'visible' to bees because they are:", we need to analyze the options provided and understand the concept of nectar guides in flowering plants.

### Step-by-Step Solution:

1. **Understanding Nectar Guides**:
- Nectar guides are specific markings or patterns found on the flowers of some angiosperm species. These markings help guide pollinators, such as bees, to the rewards (nectar and pollen) offered by the flowers.

2. **Role of Ultraviolet (UV) Light**:
- Many insects, including bees, can see ultraviolet light, which is invisible to humans. Nectar guides often have patterns that reflect UV light, making them more visible to these pollinators.

3. **Analyzing the Options**:
- **Option A**: Colorless areas which absorb the ultraviolet radiations.
- This is incorrect because nectar guides are not colorless; they are typically colored spots.
- **Option B**: Colored spots which reflect ultraviolet rays.
- This is correct as nectar guides are indeed colored spots that reflect UV rays, making them visible to bees.
- **Option C**: Colorless spots which neither absorb nor reflect ultraviolet rays.
- This is incorrect because nectar guides are not colorless.
- **Option D**: Colored spots which neither absorb nor reflect the UV rays.
- This is incorrect because nectar guides do reflect UV rays.

4. **Conclusion**:
- The correct answer is **Option B: Colored spots which reflect ultraviolet rays**. This explains why nectar guides become visible to bees.