在生理条件下合成血红素的限速步骤是合成()
A．胆色素原
B．线状四吡咯
C．原卟啉原Ⅸ
D．δ-氨基-γ-酮戊酸
E．尿卟啉原Ⅲ
参考答案：D
一He's never seen to eat so much food, ______?
一No, he always eats a little. [ ]
A. is he
B. isn't he
C. has he
D. hasn't he
关于右旋心，错误的是（）。
A.心房正位
B.心脏轴线与心尖指向右侧胸腔
C.心脏各节段与连接顺序多正常
D.心室左袢
E.内脏位置正常
