Let a and b be positive real numbers such that ab(a−b)=1. Which of the followings can a2+b2 take?<spanclass=′latex−bold′>(A)</span>1<spanclass=′latex−bold′>(B)</span>2<spanclass=′latex−bold′>(C)</span>22<spanclass=′latex−bold′>(D)</span>11<spanclass=′latex−bold′>(E)</span>None of the preceding