Which of the following is more close to a black body?

If mass-energy equivalence is taken into account, when water is cooled to form ice, the mass of water should

Cooking gas containers are kept in a lorry moving with uniform speed. The temperature of the gas molecules inside will

At what temperature is the $$r.m.s$$ velocity of a hydrogen molecule equal to that of an oxygen molecule at $${47^ \circ }C?$$