Explanation:

- Word: Plenty

- Means a large or sufficient amount of something.

- Option 1: Vastness

- Means great size or extent.

- Does not directly oppose "plenty" in terms of quantity or sufficiency.

- Option 2: Dearth

- Means a scarcity or lack of something.

- Directly contrasts with "plenty" as it signifies insufficient quantity.

- Correct Answer

- Option 3: Number

- Simply represents a count or amount.

- Does not inherently imply scarcity or abundance.

- Option 4: Mass

- Refers to a large body of matter.

- Relates to heaviness or bulk, not contradicting "plenty."