Explanation:

- Option 1: Abundance

- Abundance means having plenty of resources.

- It's not typically a cause of economic problems; rather, it would fulfill needs.

- Option 2: Convenience

- Convenience relates to ease of access or use.

- While important, it's not a root cause of economic problems.

- Option 3: Scarcity ??

- Scarcity means limited resources to meet unlimited wants.

- It's the fundamental economic problem driving supply and demand.

- Forces choices and prioritization in economies.

- Option 4: None of these

- Suggests none of the listed options are correct.

- Not applicable here as scarcity is the primary issue.

Your Answer: Option 3 - Scarcity.