A terrace floor is painted in such a way that it can cool the rooms under it.
Assertion (A): White coloured paint can be used.
Reason (R): White surface is a better emitter of heat.

The correct option is C Both (A) and (R) are true, and (R) is the correct explanation of (A).

White or light-coloured surfaces emit more heat as compared to black or dark-coloured surfaces. This is because the light-coloured surfaces reflect more heat as compared to dark-coloured surfaces.
To cool the rooms under the terrace, the terrace floor is painted with white coloured paint so that it can reflect most of the sunlight back.
Therefore, white paint can be used as it is a better emmiter of heat.