The Energy of Incident Solar Radiation Reaching the Surface of Earth

The energy of incident solar radiation reaching the surface of Earth declines toward the poles from its maximum in equatorial regions. Which of these is NOT a reason for this?

A) The tilt of Earth increases the reflection of solar radiation.
B) A given amount of solar radiation is spread over a larger area at higher latitudes.
C) Solar radiation travels a longer path through Earth's atmosphere at higher latitudes.
D) The rays of the Sun strike Earth at right angles over the equator as compared to oblique angles at the poles.