人类血液干细胞首先见于:()
A.胚外的卵黄囊血岛
B.胚外尿囊底部
C.主动脉旁胚脏壁
D.主动脉一性腺一中肾区
E.肝脏
参考答案:A
Obama had learned to use chopsticks _____ before visiting China. [ ]
A. to eat
B. to eat with
C. to eating with
D. eating
Riehl黑变病的皮损表现分哪三个期()
A.水肿期-色素沉着期-消退期
B.炎症期-色素沉着期-增生期
C.炎症期-萎缩期-恢复期
D.炎症期-色素沉着期-萎缩期
E.炎症期-增生期-萎缩期