Which of the following is `3^(@)` amine?

Options

A. `CH_(3)-underset(NH_(2))underset(|)overset(CH_(3))overset(|)C-CH_(3)`
B. `CH_(2)-overset(H)overset(|)N-CH_(3)`
C. `CH_(3)-underset(NH_2)underset(|)N-CH_(3)`
D. `H_(2)C-underset(CH_3)underset(|)N-CH_(3)`

Answer

To determine which of the given options is a tertiary amine (3° amine), we need to analyze the bonding of nitrogen in each option. A tertiary amine is characterized by having three carbon atoms directly bonded to the nitrogen atom, with no hydrogen atoms attached to the nitrogen.

### Step-by-Step Solution:

1. **Understand the Definition of Tertiary Amine**:
- A tertiary amine is defined as an amine where the nitrogen atom is bonded to three carbon atoms. This means that all three hydrogen atoms that would normally be attached to nitrogen in ammonia (NH₃) are replaced by carbon-containing groups.

2. **Analyze Each Option**:
- **Option A**: Check the structure. If nitrogen is bonded to less than three carbon atoms, it is not a tertiary amine.
- **Option B**: Similarly, check the bonding of nitrogen. If it is not bonded to three carbon atoms, it is not a tertiary amine.
- **Option C**: Again, check the bonding. If nitrogen has less than three carbon atoms attached, it is not a tertiary amine.
- **Option D**: Check the structure. If nitrogen is bonded to three carbon atoms, then this is a tertiary amine.

3. **Identify the Correct Option**:
- After analyzing all options, if **Option D** is the only one where nitrogen is bonded to three carbon atoms, then Option D is the correct answer.

### Conclusion:
- The correct answer is **Option D**, which is a tertiary amine.