Which of the following are the types of stereoisomerism ?
I. Linkage isomerism
II. Optical isomerism
III. Geometrical isomerism
IV. Ionisation isomerism
Choose the correct pair of stereoisomers.

Options

A. I and II
B. II and III
C. I and IV
D. I,II and III

Answer

To solve the question regarding the types of stereoisomerism, we need to analyze the given options and determine which of them are indeed types of stereoisomerism.

### Step-by-Step Solution:

1. **Understanding Stereoisomerism**:
- Stereoisomerism refers to isomers that have the same molecular formula and connectivity of atoms but differ in the spatial arrangement of atoms. There are two main types of stereoisomerism: optical isomerism and geometrical isomerism.

2. **Analyzing the Options**:
- **I. Linkage isomerism**: This involves different connectivity of ligands to the central metal atom. It is a type of structural isomerism, not stereoisomerism.
- **II. Optical isomerism**: This is a type of stereoisomerism where isomers are non-superimposable mirror images of each other. This is a valid type of stereoisomerism.
- **III. Geometrical isomerism**: This involves different spatial arrangements of ligands around a central atom, such as cis and trans configurations. This is also a valid type of stereoisomerism.
- **IV. Ionization isomerism**: This involves the exchange of ligands between the coordination sphere and the counter ions. It is a type of structural isomerism, not stereoisomerism.

3. **Identifying the Correct Types**:
- From the analysis, we find that the valid types of stereoisomerism from the options are:
- **II. Optical isomerism**
- **III. Geometrical isomerism**

4. **Conclusion**:
- The correct pair of types of stereoisomerism from the options given is **II and III**.

### Final Answer:
The correct pair of stereoisomers is **II. Optical isomerism and III. Geometrical isomerism**.

---