The decreasing order of the basic character is :

Options

A. `NH_3 gt CH_3NH_2 gt C_2H_5 NH_2 gt C_6 H_5 NH_2`
B. `C_2H_5 NH_2 gt CH_3NH_2 gt NH_3 gt C_6 H_5 NH_2`
C. `C_6H_5NH_2 gt C_2 H_5 NH_2 gt CH_3 NH_2 gt NH_3`
D. `CH_3NH_2 gt C_2H_5NH_2 gt C_6 H_5 NH_2 gt NH_3`

Answer

To determine the decreasing order of basic character among Ammonia (NH₃), Methylamine (CH₃NH₂), Ethylamine (C₂H₅NH₂), and Aniline (C₆H₅NH₂), we need to analyze the factors that influence the basicity of these compounds.

### Step-by-Step Solution:

1. **Understanding Basicity**: Basicity refers to the ability of a compound to accept protons (H⁺ ions). In amines, the nitrogen atom has a lone pair of electrons that can be donated to a proton, making it a Lewis base.

2. **Effect of Alkyl Groups**: Alkyl groups (like methyl and ethyl) exhibit a +I (inductive) effect, which increases the electron density on the nitrogen atom. This makes the lone pair more available for donation, thereby increasing basicity.

3. **Comparing Ethylamine and Methylamine**:
- **Ethylamine (C₂H₅NH₂)**: The ethyl group has a stronger +I effect compared to the methyl group. This means that ethylamine will have a higher basicity than methylamine due to increased electron density on nitrogen.
- **Methylamine (CH₃NH₂)**: The methyl group also has a +I effect, but it is weaker than that of the ethyl group.

4. **Comparing Ammonia**:
- **Ammonia (NH₃)**: Ammonia has no alkyl groups to enhance its basicity through the +I effect. Its basicity is lower than that of both ethylamine and methylamine.

5. **Analyzing Aniline**:
- **Aniline (C₆H₅NH₂)**: In aniline, the lone pair on nitrogen is delocalized into the aromatic ring through resonance. This delocalization reduces the availability of the lone pair for protonation, making aniline less basic than ammonia, methylamine, and ethylamine.

6. **Final Order of Basicity**:
- Based on the above analysis, the order of basicity from highest to lowest is:
1. Ethylamine (C₂H₅NH₂)
2. Methylamine (CH₃NH₂)
3. Ammonia (NH₃)
4. Aniline (C₆H₅NH₂)

### Conclusion:
The decreasing order of basic character is:
**Ethylamine > Methylamine > Ammonia > Aniline**