Which is the most common oxidation state of lanthanoids?

Explanation

To determine the most common oxidation state of lanthanoids, we can follow these steps:

### Step 1: Understand the Lanthanoids
Lanthanoids are a series of 15 elements from Lanthanum (La) to Lutetium (Lu) in the periodic table. They are known for their similar properties and electronic configurations.

**Hint:** Remember that lanthanoids are f-block elements and have specific trends in their oxidation states.

### Step 2: Analyze the Electronic Configuration
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