Which of the following is correct about insolation? I. It influences…

Insolation is the incoming solar radiation received at Earth's surface, and it is the primary source of energy that heats the atmosphere and the land/ocean surface. Because this energy input is not the same everywhere, the amount of insolation a location intercepts is the single biggest control on how temperature is distributed across latitudes.

The insolation received at any latitude depends chiefly on the angle at which sunlight strikes the surface and the length of atmospheric path the rays travel through before reaching the ground. Near the equator, the sun's rays fall at a high angle (close to vertical) and travel a short atmospheric path, so a given beam of sunlight stays concentrated over a small area and loses little energy en route — insolation is therefore highest here. Moving from the equator toward the poles, the angle of incidence keeps decreasing, spreading the same energy over a progressively larger surface area while the rays also pass through a longer stretch of atmosphere, so insolation steadily falls rather than rising.

• “Only II” claims insolation rises from the equator toward the poles — the actual gradient runs the opposite way (highest at the equator, lowest at the poles), so this option's core claim about the direction is inverted.

• “Both I and II” correctly credits insolation with shaping temperature distribution, but it pairs that with the same inverted poleward-increase claim, so it still fails on the second statement.

• “Neither I nor II” wrongly denies insolation any role in temperature distribution, overlooking that it is the fundamental energy input that drives surface heating in the first place.

Since insolation genuinely governs how temperature is distributed (the first statement holds) while it decreases — not increases — from the equator to the poles (the second statement fails), only the first statement is correct.