All of these would be perfectly fine represented by a pie chart except A, which doesn't add to 100%.
The question seems to be getting at the idea that a pie chart might be better when the slices are all visually different sizes. I don't really think that's right; a pie chart for D say, where the two slices are about the same, gives the correct impression of the relative frequencies, which are about the same.
Answer they're looking for: C
