B. Is the sentence with a comma error
The way in which Faustus uses his powers is increasingly evil.
The answer is C, I believe. Hope this helps!
Using the formula:

Which is, 3.14 x 2^2 (radius is half of diameter)
Which equals 12.56.
Before beginning an Internet search to find supporting information for your topic, you must know C. what type of information you're looking for.