The common featrues among the species `CN^(-), CO and CO^(+)` are

Options

A. Bond order three and isoelectronic
B. Bond order three and weak-field ligands
C. Bond order two and `pi-`acceptor
D. Isoelectronic and weak-field ligands

Explanation

To determine the common features among the species CN^(-), CO, and CO^(+), we will analyze their electronic configurations, bond orders, and other relevant properties.

### Step-by-Step Solution:

**Step 1: Determine the total number of electrons for each species.**

- **For CN^(-)**:
- Carbon (C) has 6 electrons.
- Nitrogen (N) has 7 electrons.
- The negative charge (-1) indicates an additional electron.
- Total electrons = 6 (C) + 7 (N) + 1 (extra electron) = 14 electrons.

- **For CO**:
- Carbon (C) has 6 electrons.
- Oxygen (O) has 8 electrons.
- Total electrons = 6 (C) + 8 (O) = 14 electrons.

- **For CO^(+)**:
- Carbon (C) has 6 electrons.
- Oxygen (O) has 8 electrons.
- The positive charge (+1) indicates one less electron.
- Total electrons = 6 (C) + 8 (O) - 1 (lost electron) = 13 electrons.

**Step 2: Calculate the bond order for each species.**

- **Bond Order Formula**:
\[ \text{Bond Order} = \frac{\text{Number of bonding electrons} - \text{Number of antibonding electrons}}{2} \]

- **For CN^(-)**:
- Total electrons = 14.
- Bond order = 3.0.

- **For CO**:
- Total electrons = 14.
- Bond order = 3.0.

- **For CO^(+)**:
- Total electrons = 13.
- Bond order = 2.5.

**Step 3: Identify common features.**

- **Common Electron Count**:
- CN^(-) and CO both have 14 electrons, while CO^(+) has 13 electrons.

- **Bond Order**:
- CN^(-) and CO both have a bond order of 3.0, while CO^(+) has a bond order of 2.5.

- **Isoelectronic Species**:
- CN^(-) and CO are isoelectronic (same number of electrons), but CO^(+) is not.

- **Ligand Field Strength**:
- CN^(-) is a weak field ligand, while CO is a strong field ligand.

### Conclusion:
The common features among CN^(-), CO, and CO^(+) are:
1. CN^(-) and CO are isoelectronic (both have 14 electrons).
2. CN^(-) and CO have a higher bond order (3.0) compared to CO^(+) (2.5).
3. They all involve carbon and nitrogen/oxygen in their structures.