Which of the following orbitals are possible ?
`1s, 2s, 3f, 3d`

Explanation

To determine which of the given orbitals are possible, we need to analyze each orbital based on the quantum numbers associated with them. The quantum numbers are:

1. **Principal Quantum Number (n)**: Indicates the main energy level or shell.
2. **Azimuthal Quantum Number (l)**: Indicates the subshell (s, p, d, f) and can take values from 0 to (n-1).
- l = 0 corresponds to s orbitals
- l = 1 corresponds to p orbitals
- l = 2 corresponds to d orbitals
- l = 3 corresponds to f orbitals
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