Which one of the following complexes exhibit chirality?

Options

A. `[Cr(o x)_(3)]^(3)`
B. `cis-[PtCl_(2)(en)]`
C. `cis-[RhCl_(2)(NH_(3))_(2)]^(-)`
D. `mer-[Co(NO_(2))_(3)("trien")]`

Explanation

To determine which of the given complexes exhibit chirality, we need to understand the concept of chirality and optical isomerism. Chirality refers to the property of a molecule that makes it non-superimposable on its mirror image, which is a characteristic of optically active compounds.

### Step-by-Step Solution:

1. **Understand Chirality**:
- Chirality is a property of a molecule that lacks a plane of symmetry. If a molecule can be superimposed on its mirror image, it is achiral. If it cannot, it is chiral.

2. **Identify the Complexes**:
...