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.

Heat in a liquid is transferred by:

1. conduction
2. convection
3. radiation
4. conduction and radiation

The vacuum kept in between the walls of a thermos flask reduces the heat transfer by:

1. conduction only
2. convection only
3. radiation only
4. conduction and convection

Assertion (A): A reading of 32 °F on a thermometer equals 0 °C.

Reason (R): The Celsius scale is commonly used in most countries for measuring temperature.

1. Both A and R are true and R is the correct explanation of A
2. Both A and R are true and R is not the correct explanation of A
3. A is true but R is false
4. A is false but R is true