Arrange the following in the decreasing order of their basic strength :
i. `PhNH_2` ii.` EtNH_2 ` iii. `Et_2NH` iv, `NH_3`

Explanation

To arrange the given compounds in the decreasing order of their basic strength, we need to analyze the ability of each compound to donate its lone pair of electrons. The basic strength is influenced by the electron-donating or withdrawing effects of substituents attached to the nitrogen atom.

### Step-by-Step Solution:

1. **Identify the Compounds**: We have four compounds to analyze:
- i. `PhNH2` (Aniline)
- ii. `EtNH2` (Ethylamine)
- iii. `Et2NH` (Diethylamine)
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