Arrange the following in the decreasing order of their basic strength in aqueous solutions :
`CH_(3)CSNH_(2),(CH_(3))_(2)NH, (CH_(3))_(3) N` and `NH_(3)`

Explanation

To arrange the compounds `CH₃CSNH₂`, `(CH₃)₂NH`, `(CH₃)₃N`, and `NH₃` in decreasing order of their basic strength in aqueous solutions, we can follow these steps:

### Step 1: Identify the Types of Amines
- `CH₃CSNH₂` is a primary amine (with one alkyl group).
- `(CH₃)₂NH` is a secondary amine (with two alkyl groups).
- `(CH₃)₃N` is a tertiary amine (with three alkyl groups).
- `NH₃` is ammonia, which can be considered a primary amine with no alkyl groups.

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