Animals undergo inactive stage during winter is known as:

Options

A. aestivation
B. hibernation
C. adaptation
D. acclimatisation

Explanation

To answer the question "Animals undergo inactive stage during winter is known as:", we will analyze the options provided and identify the correct term.

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks for the term that describes the inactive stage that animals enter during the winter season.

2. **Reviewing the Options**: The options given are:
- A) Estivation
- B) Hibernation
- C) Adaptation
- D) Acclimatization

3. **Defining Each Term**:
- **Estivation**: This is a period of dormancy that occurs during hot or dry conditions, typically in the summer. This option does not relate to winter.
- **Hibernation**: This is a state of inactivity and metabolic depression in animals during the winter months. It is characterized by a significant reduction in body temperature, heart rate, and metabolic rate.
- **Adaptation**: This refers to the process by which organisms adjust to their environment to improve their chances of survival. It is not specifically related to a dormant state.
- **Acclimatization**: This is a gradual process where an organism adjusts to changes in its environment, but it does not refer to a dormant state.

4. **Identifying the Correct Answer**: Since the question specifically refers to the inactive stage during winter, the correct term is **Hibernation** (Option B).

5. **Final Answer**: Therefore, the answer to the question is **Hibernation**.