用于治疗恶心贫血：
A．维生素B12
B．红细胞生成素
C．右旋糖酐
D．硫酸亚铁
E．维生素B6
参考答案：A
Is it the fact ____ he hasn't turned in his research report?[ ]
A. whether
B. that
C. which
D. why
