Which statement is correct:

1. Iron rims are cooled before they are placed on cart wheels.
2. A glass stopper gets tight on warming the neck of the bottle.
3. Telephone wires sag in winter, but becomes tight in summer.
4. A little space is left between two rails on a railway track.

A little space is left between two rails on a railway track

Reason — A little space is left between two rails on a railway track to allow expansion of rails during summer otherwise rails will bend sideways.