Liquid nitrogen and monitor: what they have in common

1. Step 1. Liquid nitrogen — is used in — Dewar flask. Storage.
2. Step 2. Dewar flask — uses — Vacuum. A vacuum.
3. Step 3. Vacuum — is used in — Cathode-ray tube. Inside is a vacuum.
4. Step 4. Cathode-ray tube — is part of — Monitor. The first monitors were CRTs.

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