肝癌实验室检查项目中，最常用和最有价值的是（）
A.γ-谷氨酰转肽酶
B.血清碱性磷酸酶
C.岩藻糖苷酶
D.甲胎蛋白
E.癌胚抗原
参考答案：D
He has to do his homework now, _______? [ ]
A. has he
B. hasn't him
C. does he
D. doesn't he
作出图1中小球受浮力的示意图，图2中最省力的绕线方法，图3中F的力臂．
