An example of long term adaptation is

Options

A. hibernation
B. melanism
C. aestivation
D. spines of cactus

Answer

### Step-by-Step Solution:

1. **Understanding Adaptations**:
- Adaptations are characteristics that enhance the survival and reproduction of organisms in their environments. They can be classified into two categories: long-term adaptations and short-term adaptations.

2. **Identifying Long-Term vs. Short-Term Adaptations**:
- **Long-term adaptations** are evolutionary changes that occur over many generations, leading to significant changes in a species.
- **Short-term adaptations** are immediate responses to environmental changes that help an organism survive in the short run.

3. **Analyzing the Options**:
- **Hibernation**: This is a short-term adaptation that allows animals to survive cold temperatures by entering a state of dormancy. It is not a long-term adaptation.
- **Melanism**: This refers to the dark pigmentation in organisms, which can help with camouflage. It is also considered a short-term adaptation for survival and not a long-term evolutionary change.
- **Activation**: This term generally refers to a short-term response to environmental stress, such as heat or scarcity, and is not a long-term adaptation.
- **Spines of Cactus**: These are modifications of leaves that have evolved over time to help cacti survive in arid environments by reducing water loss and providing protection from herbivores. This is a clear example of a long-term adaptation.

4. **Conclusion**:
- Among the options provided, the spines of cactus represent a long-term adaptation. Therefore, the correct answer is **spines of cactus**.

### Final Answer:
The correct answer is **spines of cactus**.

---