The Sun's total energy output that reaches the Earths surfce is:
a) 5%
b)0.5%
c)0.05%
d)0.005%
e)0.0005%

This can be closely estimated by treating Earth's orbit with the Sun
as an ideal circle. It is sufficiently close to a circle to be a
useful approximation.

   The use your search engine to retrieve the following:
[1]- Earth's distance from the Sun,
[2]- the mensuration formula for calculatng the surface area of a
sphere, given the sphere's radius,
[3]- Earth's diameter,
[4]- the mensuration formula for the area of a circle.

   Earth's orbital radius is the radius of a very large sphere
centered upon the Sun. Compute the area of that sphere.

   Earth's cross-sectional area is given by plugging its diameter into
the formula for the area of a circle. Compute this cross-sectional
area.

   Now, divide Earth's cross-sectional area by the area of the giant
SDun-centered sphere. This will yield the fraction of the Sun's output
which falls on Earth.

   This information is sufficient to guide you to a useful answer.
Other than that, no one is here to spoon-feed you the answers to your
homework.

This looks like the right way to get the answer. I didn't check the math.

http://www.madsci.org/posts/archives/May2003/1051835154.Es.r.html

the suns enegry that reaches the earht surface is 0.0005% of the total
energy that is dissipated by sun. for the caliulation of ths we have
to know the radius of earth,sun. the entire sun's energy that reaches
the earth is also not observed by the earth. the earths stratosphere
acts as a shield and mostly reples the solar enegy of which is comic
rays.the ozone layer is the best thing that mostly reples the suns
energy that reaches the earth. if its not there then we will not have
been orginated now.