Answer, and give a reason. A metal lid on a glass jar is stuck.

Step 1. (a) Metal expands more than glass, and the hot water warms the lid first, so the lid grows away from the glass.

Step 2. (b) In winter the wires shrink; without slack they would pull tight and could snap.

Step 3. (c) Heat the ring: its hole grows with it. Once on and cooled, it grips the rod tightly.