3岁小儿在玩时，不慎将纽扣误吸进入气管，急诊入院，治疗小儿气管与支气管异物唯一有效的治疗方法是（）。

A.拍背

B.将小儿倒立

C.刺激咽部

D.给腹部加压

E.内镜下取出异物

Which of the following statements regarding mortgage-backed securities (MBS) and collateralized mortgage obligations (CMOs) is most likely correct（）

A. MBS are created from CMOs.

B. Creating CMOs does not reduce the overall prepayment risk of a mortgage pass through security.

C. The prepayment option of an MBS benefits the security holder.