Explanation:

- The sentence discusses "black marketers hoarding large quantities of groceries." This context implies accumulating supplies in secret or for a future purpose.

- Doling Out: Means distributing or giving out items. It is the opposite of hoarding.

- Designing: Involves creating or planning something. Not related to gathering or storing.

- Training Up: Refers to teaching or preparing someone with skills, unrelated to collecting items.

- Piling Up: Means accumulating or stacking items, similar to hoarding.

- Correct Answer: Piling Up