Insolation refers to

Answer: (c) Exposure to the rays of sun

Insolation = incoming solar radiation reaching the Earth.

The idea

Insolation is incoming solar radiation received at a surface or at the top of the atmosphere. It is an energy input from the Sun. The Earth’s outgoing infrared radiation is a different flow. The word resembles “insulation”, but the two refer to different physical ideas.

Why the others are wrong

(a) That is electrical insulation.

(d) Too vague — insolation is solar radiation specifically.

The trap

Insolation vs insulation.

Elimination technique

Expand the term as incoming solar radiation. It identifies exposure to the Sun’s rays specifically, whereas generic light exposure is too broad and restraining current or water describes unrelated processes.

Also know

Sun angle, day length, clouds and atmospheric transparency affect surface insolation. A slanting beam spreads over a larger area and passes through more atmosphere than a nearly overhead beam. Albedo gives the fraction reflected, so received radiation and absorbed radiation are not identical. Earth’s axial tilt changes the seasonal distribution of sunlight.