体内缺铁时的最早表现是
A．血清铁降低
B．贮存铁减少
C．红细胞平均血红蛋白量降低
D．红细胞平均体积变小
E．血清总铁结合力增高
参考答案：B
— What are you doing? — [ ]
A. I write a letter.
B. I am cooking.
C. I am tired.
t1/2约为8.5h：
A．四环素B．多西环素C．二者均是D．二者均否
