''$A$ perfect black body is black in colour.'' Is this statement true or false?

The coefficient of absorption $(a)$ and the coefficient of reflection $(r)$ of a thin uniform plate are $0.77$ and $0.17$ respectively. If $250 \ kcal$ of heat is incident on the surface of the plate,the quantity of heat transmitted $(t)$ is: (in $kcal$)

The graph shown in the adjacent diagram represents the variation of temperature $(T)$ of two bodies,$x$ and $y$,having the same surface area,with time $(t)$ due to the emission of radiation. Find the correct relation between their emissivities $(e)$ and absorptive powers $(a)$.

When we enter an air-conditioned room,we feel cold. This can be explained by:

Two thermometers $A$ and $B$ are exposed to sunlight. The bulb of $A$ is painted black,but that of $B$ is not painted. Which of the following statements is correct regarding this case?

What would happen if the greenhouse effect were not present?