Payment card and sewage treatment plant: what they have in common

1. Step 1. Payment card — is made of — Polyvinyl chloride (PVC). The card is PVC.
2. Step 2. Polyvinyl chloride (PVC) — is material for — Catheter. Plastic catheters.
3. Step 3. Catheter — is part of — IV drip. A catheter.
4. Step 4. IV drip — uses — Gravity flow. The solution flows under gravity.
5. Step 5. Gravity flow — is used in — Sewerage. Waste water flows down a gradient.
6. Step 6. Sewerage — has part — Sewage treatment plant. Treatment plants.

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