The 'epimerisation' involves

Options

A. Change in configuration
B. Addition of one more'C
C. Subtraction of a 'C
D. Conversion of -CHO to -C=O

Answer

### Step-by-Step Solution:

1. **Definition of Epimerization**:
- Epimerization is a specific type of stereoisomerism where two compounds, known as epimers, differ in configuration at only one specific chiral center.

2. **Understanding Chiral Centers**:
- A chiral center (or chiral carbon) is a carbon atom that is attached to four different groups. The configuration of these groups can vary, leading to different stereoisomers.

3. **Formation of Epimers**:
- During epimerization, the configuration at one chiral center changes, resulting in the formation of two distinct compounds that are epimers of each other. The rest of the structure remains unchanged.

4. **Example of Epimers**:
- A common example of epimers is glucose and galactose. Both are sugars that differ only at one chiral center, which makes them epimers.

5. **Conclusion**:
- Therefore, epimerization involves a change in configuration at one chiral center, leading to the formation of epimers.