28. We finished the run in less than half the time ____. 　　　(A) allowing (B) to allow 　　　(C) allowed (D) allows

31. It was announced that only when the fire was under control ___ to return to their homes. 　　　(A) the residents would be permitted 　　　(B) had the residents been permitted 　　　(C) would be residents be permitted 　　　(D) the residents had been permitted 　　　