Physics
Water pipes in hilly areas often burst on a cold frosty night, because

The material of which pipes are made contracts due to cold and so breaks
Water in the pipes freezes and on freezing water expands, so pipes break
None of these
Frost makes the pipes rusty, so they break

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Physics
A stone floor feels cold to the bare feet but a carpet on the same floor feels warm. This is because

The carpet is a better conductor of heat than the stone
The stone conveys the heat away from the feet more rapidly than the carpet
The human body maintains a constant temperature
The floor and carpet are at different temperatures

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