Which of the following statements are correct?

Options

A. (a) Diastereomers have different physical properties but not identical chemical properties.
B. (b) Enantiomers have the same physical and chemical properties but different physiological properties.
C. (c) Polarimeter is used in measuring the optical rotation of compund.
D. Only organic molecules show optical isomerism.

Explanation

To determine which of the statements regarding isomerism are correct, let's analyze each statement one by one:

### Step-by-Step Solution:

1. **Statement A: Diastereomers have different physical properties but not identical chemical properties.**
- **Analysis:** Diastereomers are stereoisomers that are not mirror images of each other. They have different physical properties (like melting points and boiling points) and can also exhibit different chemical properties. Therefore, this statement is correct.
- **Conclusion:** **Correct.**

2. **Statement B: Enantiomers have the same physical and chemical properties but differ in terms of physiological properties.**
- **Analysis:** Enantiomers are non-superimposable mirror images of each other and typically have identical physical and chemical properties. However, they can have different physiological effects when interacting with biological systems. For example, one enantiomer of a drug may be therapeutic while the other may be harmful. Thus, this statement is also correct.
- **Conclusion:** **Correct.**

3. **Statement C: A polarimeter is used to measure the optical rotation of the compound.**
- **Analysis:** A polarimeter is indeed an instrument used to measure the angle of rotation of polarized light as it passes through an optically active substance. This statement is accurate.
- **Conclusion:** **Correct.**

4. **Statement D: Only organic compounds show optical isomerism.**
- **Analysis:** This statement is false. While many organic compounds exhibit optical isomerism, inorganic compounds, particularly coordination compounds, can also show optical isomerism. For instance, certain metal complexes can exist in optically active forms. Therefore, this statement is incorrect.
- **Conclusion:** **Incorrect.**

### Final Answer:
The correct statements are **A, B, and C**.