Variability in the oxidation states of lanthanides is limited. Why? 

Explanation

### Step-by-Step Solution:

1. **Understanding Oxidation States**:
- Oxidation states refer to the charge of an atom in a compound, which indicates how many electrons have been lost or gained. In lanthanides, the common oxidation state is +3.

2. **Nature of Lanthanides**:
- Lanthanides are inner-transition elements located in the f-block of the periodic table. They have partially filled 4f orbitals.

...