Two question from SAT 1. Vigorous student debate with(A) the problem of steeply increased(B) student activity fees has caused (C)many people to take a critical look at the activities those fees support(D). "debate with" is wrong, I can feel it's not correct, but how to correct it? What’s the problem here? 2.Pictures of vipers drawn on(A) the walls of caves suggest(B) that prehistoric hunters may have used(C) snake charms for bringing(D) good luck. "for bringing" is wrong. But “use A for doing B”is correct, right? So why is the answer D? What’s the difference between “use A to do” and “use A for doing B”?