More and more teaching _______ are being developed across the globe, which are sure to _______to    make classroom teaching more lively and interesting.      [ ]

A. aids; help      

B. assistance; help    

C. aids; assist    

D. helps; aid

哪一种胎位分娩对母亲最不利？（）

A．枕后位

B．枕前位

C．单臀

D．枕横位

E．横位