Solar Eclipses (When the Moon and Sun Are Precisely in Line)

Solar eclipses (when the Moon and Sun are precisely in line) can be either total (Sun completely covered) or annular (Sun not quite covered) when viewed from the eclipse centerline. This is because

A) the Moon has deep valleys on its surface.
B) the Moon's orbit is inclined at several degrees to that of Earth.
C) the Moon's distance from Earth varies from eclipse to eclipse.
D) of the time of day at the viewing site; annular eclipses always occur in early mornings and early evenings.