A.5% B.10% C.15% D.20%
A.真皮 B.基底細(xì)胞層 C.血管周圍 D.顆粒層
A.中胚層的神經(jīng)嵴 B.中胚層的神經(jīng)管 C.外胚層的神經(jīng)嵴 D.外胚層的神經(jīng)管