If 2a+2b=3c+3d, the number of integers a,b,c,d which can possibly be negative, is, at most:<spanclass=′latex−bold′>(A)</span>4<spanclass=′latex−bold′>(B)</span>3<spanclass=′latex−bold′>(C)</span>2<spanclass=′latex−bold′>(D)</span>1<spanclass=′latex−bold′>(E)</span>0