Hi all - hoping this screenshot uploaded correctly. This problem was discussed in the recorded session I just watched for Geometry.

Greg’s explanation was to maximize the possible area of the quadrilateral within the square by moving points B & D down to form a square, which would create an area of 50 and make the problem have an answer of D.

For me, I’m so confused because I can’t see any reason why we’d be allowed to assume that a line drawn from A to C is actually the diameter of the circle. Nothing is specified in the question about whether or not the distance from A to C crosses the center of the circle. If I’m not mistaken, isn’t that the only scenario wherein his strategy is possible?

Shouldn’t this be D simply from the realization that we can’t verify if the distance from A to C is actually the diameter?

Thanks for any input & I hope I’m not the only one who got tripped up by this one.