Question

Ricardo wanted to see what container would keep his hot chocolate warm for the longest time. The table below shows his results:
Container Warm or Cold After 5 Hours?
Glass Cold
Plastic Cup Cold
Thermos Warm
Paper Cup Cold
What could Ricardo conclude from his experiment?
None of these containers is good for keeping something warm.
A thermos is the worst container for keeping something warm.
A paper cup is the best container for keeping something warm.
A thermos is the best container for keeping something warm.