Explanation:

- State of being full or complete:

- This implies a condition where nothing is lacking, everything necessary is present.

- Option 1: Plunder:

- Refers to stealing goods, typically using force and in a time of war or civil disorder.

- Not related to completeness.

- Option 2: Plebiscite:

- Refers to a direct vote by eligible voters to decide an important public question.

- Unrelated to fullness or completeness.

- Option 3: Plenitude:

- Means abundance, completeness, or the state of being full.

- Correct Answer for the given group of words.

- Option 4: Pliability:

- Relates to flexibility or the condition of being easily bent or influenced.

- Not associated with fullness or completeness.