抽取胎儿血液不能诊断（）
A.镰状细胞贫血
B.血友病
C.脊柱裂
D.半乳糖血症
E.地中海贫血
参考答案：C
—How long do you think it is ________ he arrived here?
—No more than half a year, I believe.
A．when
B．that
C．before
D．since
数据库的功能
