The Uneven Distribution of Insolation by Latitude Is Primarily a Result

Multiple Choice

The uneven distribution of insolation by latitude is primarily a result of

A) variability in the Sun's output.
B) the changing distance of Earth from the Sun.
C) variation in the value of a watt.
D) Earth's sphericity,which presents varied angles to parallel solar rays.
E) the longterm decrease in the Sun's energy output.