Complete the following analogy:
Two different electron donor site (A) :: Inversion of configuration:

Options

A. A : ambidentate nucleophile `B: S_(N)^(2)` reaction.
B. A: Bidentate nucleophile B: `S_(N)^(1)` reaction
C. A: Unidentate nucleophile B: `E_1` reaction
D. A : Polydentate Nucleophile B : Substitution reaction

Explanation

To complete the analogy "Two different electron donor site (A) :: Inversion of configuration (B)", we need to understand the relationship between the two concepts presented.

### Step-by-Step Solution:

1. **Understanding Electron Donor Sites**:
- In coordination chemistry, ligands can have multiple donor sites. A ligand with two different electron donor sites is known as a bidentate ligand. For example, in oxalate (C2O4^2-), both oxygen atoms can act as donor sites.

2. **Identifying the Concept of Inversion of Configuration**:
- Inversion of configuration typically refers to a change in the spatial arrangement of atoms around a central atom, often seen in chiral molecules. This is commonly observed in reactions such as SN2, where the nucleophile attacks from the opposite side of the leaving group, leading to inversion of configuration.

3. **Connecting the Concepts**:
- The relationship can be drawn between the number of donor sites in a ligand and the type of reaction mechanism that involves inversion of configuration. Just as a bidentate ligand can coordinate to a metal center through two different sites, certain reaction mechanisms (like SN2) involve a change in configuration due to the nature of the nucleophile's attack.

4. **Conclusion**:
- Therefore, we can complete the analogy as follows:
- "Two different electron donor site (A) :: Bidentate ligand (B) :: Inversion of configuration (C) :: SN2 reaction mechanism".

### Final Analogy:
- "Two different electron donor site (A) : Bidentate ligand :: Inversion of configuration (B) : SN2 reaction mechanism".