37 (A) keep (B) permit (C) vanish (D) negotiate

47 According to the passage, which of the following explains why rabbits chew their food in a circular direction? (A) It helps them develop stronger jaws and sharpen their teeth. (B) It helps them avoid developing unnecessary stronger jaws and teeth. (C) It provides opportunities for them to chew quietly in the wild. (D) It brings all their teeth into wear and keeps them at the right length.