Answers: A and C-Both orange and brown lenses would be the optimum lens color for a tennis player.
Orange or brown lenses will pick up the color of the yellow ball better, provide more contrast and still give the darkness needed for a sunglass. Additionally these lenses should be polarized to completely eliminate glare from tennis court surfaces and annoying glare from surrounding surfaces.
Yellow will give the needed contrast but will not be dark enough to prevent squinting. A gray color will not give as much contrast as either orange or brown.