A total solar eclipse occurs when the moon passes completely in front of the sun. There are
five phases of a total solar eclipse. During the
first phase, the partial eclipse phase, the moon
begins to pass in front of the sun, blocking a
fraction of it. Second, the total eclipse phase
begins and the moon blocks the light from the
sun when viewed from a specific location. The
third phase, called the totality, is the specific
point when the moon completely covers the sun.
In this phase, the sky becomes dark as the
umbra, or complete shadow of the moon, totally
hides the sun's rays, bathing the earth in
darkness. In one of the most dramatic elements
of a total solar eclipse, the sun's corona, or upper
atmosphere, shines all around the moon, which
appears black against the fiery halo of the
corona. During the fourth phase, the total eclipse
ends when the moon begins to move away from
the sun and the sky lightens. Finally, in the fifth
phase, the moon moves completely out of line
with the sun and the eclipse ends.
Which of these best states the main idea?

a. The third phase, called the totality, is the
specific point when the moon completely covers
the sun.

b. During the fourth phase, the total eclipse ends
when the moon begins to move away from the
sun and the sky lightens.

c. There are five phases of a total solar eclipse.

d. In one of the most dramatic elements of a total
solar eclipse, the sun's corona, or upper
atmosphere, shines all around the moon, which
appears black against the fiery halo of the
corona.