Source: GMAT Prep, mba.com, exam II

I got this question correct by process of elimination as well as drawing it out and making an educated guess. I would like to understand if there is a solid reason (math rule) for this answer. If anyone can help, that would be great.

What is the greatest possible area of a triangular region with one vertex at the center of a circle of radius 1 and the other two vertices on the circle?

a. rt3/4

b. 1/2

c. Pi/4

d. 1

e. rt2

I will post the correct answer later (for those of you wishing to try it without seeing the answer first).

Thank you!