Study the given correlation.
Heat treatment : Sterilisation :: Vaccination : X
Here, X refers to

Options

A. Pasteurisation
B. Immunisation
C. Fertilisation
D. Inoculation

Explanation

To solve the correlation given in the question, we need to analyze the relationship between the terms provided.

### Step-by-Step Solution:

1. **Understanding the First Pair**:
- The first part of the correlation is "Heat treatment : Sterilisation". Here, heat treatment is a method used to achieve sterilization. Sterilization is the process of making something free from bacteria or other living microorganisms.

2. **Identifying the Second Pair**:
- We need to find a term that correlates with "Vaccination" in a similar way that "Sterilisation" correlates with "Heat treatment".

3. **Understanding Vaccination**:
- Vaccination is a process where a vaccine is introduced into the body to stimulate the immune system. The primary purpose of vaccination is to provide immunity against specific diseases.

4. **Finding the Correct Term for X**:
- The options provided are:
- A) Pasteurization
- B) Immunization
- C) Fertilization
- D) Inoculation
- Among these options, "Immunization" is the process that results from vaccination. When a person is vaccinated, they become immunized against a particular disease.

5. **Conclusion**:
- Therefore, the correct answer for X, which correlates with "Vaccination", is "Immunization".

### Final Answer:
X refers to **Immunization**.