单项选择题
A.40%,50% B.50%,40% C.30%,60% D.60%,30%
A.肾脏 B.脾脏 C.肝脏 D.胃
A.形成胎盘 B.排卵 C.受精卵着床 D.将受精卵孕育成胎儿并完成分娩