What is the product of real numbers a which make x2+ax+1 a negative integer for only one real number x?<spanclass=′latex−bold′>(A)</span>−1<spanclass=′latex−bold′>(B)</span>−2<spanclass=′latex−bold′>(C)</span>−4<spanclass=′latex−bold′>(D)</span>−6<spanclass=′latex−bold′>(E)</span>−8