The function f satisfies f(x)+3f(1−x)=x2 for every real x. If S={x∣f(x)=0}, which one is true?<spanclass=′latex−bold′>(A)</span>S is an infinite set.<spanclass=′latex−bold′>(B)</span>{0,1}⊂S<spanclass=′latex−bold′>(C)</span>S=ϕ<spanclass=′latex−bold′>(D)</span>S={(3+3)/2,(3−3)/2}<spanclass=′latex−bold′>(E)</span> None of above