With our country entering ________ ageing society, there will be ________ rise in the demand for nursing staff.[ ]

A. the; the

B. an; /

C. /; a

D. an; a

在胚胎发育过程中，有羊膜和羊水出现的动物是[ ]

A．蝗虫和蚯蚓

B．猪和鸭

C．鱼和狗

D．青蛙和蛇