25.Olivia: What’s the biggest source of pollution? The answer might surprise you. Fenny: Plastic bags? Olivia: No, throwaway diapers. Fenny: But how come they became a source of pollution? Olivia: _______________    
(A) About fifty years ago.
(B) They don’t break down easily.
(C) Cotton diapers are good for the environment.
(D) People are using fewer throwaway diapers.