The comopound which exhibits coordination isomerism is:

Options

A. `[Pt(NH_3)_2Cl_2]`
B. `K_3[Fe(CN)_6]`
C. `K_4[Fe(CN)_6]`
D. `[Cr(NH_3)_6][Co(CN)_6]`

Explanation

To determine which compound exhibits coordination isomerism from the given options, we need to understand what coordination isomerism is and analyze the compounds provided.

### Step-by-Step Solution:

1. **Understand Coordination Isomerism**:
Coordination isomerism occurs when there are two or more isomers that have the same molecular formula but differ in the arrangement of ligands around the central metal ion. This typically involves a cationic and an anionic part in the coordination complex.

2. **Identify the Given Compounds**:
The compounds provided are:
- PTNH3O2I
- Cl2
- K3Fe(CN)6
- K4Fe(CN)6
- Cr(NH3)6
- Co(CN)6

3. **Analyze Each Compound for Coordination Isomerism**:
- **PTNH3O2I**: This compound does not have a clear cationic and anionic part, thus it is unlikely to exhibit coordination isomerism.
- **Cl2**: This is a simple diatomic molecule and does not exhibit coordination isomerism.
- **K3Fe(CN)6**: This is a coordination compound with a cation (K+) and an anion (Fe(CN)6)3-. It has the potential for coordination isomerism.
- **K4Fe(CN)6**: Similar to K3Fe(CN)6, this compound also has a cation and an anion, thus it may exhibit coordination isomerism.
- **Cr(NH3)6**: This is a neutral complex with no distinct cationic or anionic parts, so it does not exhibit coordination isomerism.
- **Co(CN)6**: This is also a neutral complex and does not exhibit coordination isomerism.

4. **Conclusion**:
Among the given compounds, K3Fe(CN)6 and K4Fe(CN)6 are the only ones that can exhibit coordination isomerism due to the presence of both cationic and anionic parts.

5. **Final Answer**:
The compound which exhibits coordination isomerism is **K3Fe(CN)6** and **K4Fe(CN)6**.