23. Isn’t it amazing how the human body heals ____ after an injury? 　　　(A) himself (B) him 　　　(C) itself (D) it

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 　　　