Select monoatomic, diatomic and triatomic molecules from the following list:
`He, H_(2), CO_(2), HCI, NO ,Ar, N_(2),H_(2)O`

Explanation

To classify the molecules from the given list into monoatomic, diatomic, and triatomic categories, we can follow these steps:

### Step 1: Understand the Definitions
- **Monoatomic molecules**: These are molecules that consist of a single atom.
- **Diatomic molecules**: These are molecules that consist of two atoms.
- **Triatomic molecules**: These are molecules that consist of three atoms.

### Step 2: Analyze Each Molecule
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