I took mathematics and physics because I think that ________ very important for me to make further research in this field.

A．what is

B．they are

C．this

D．which are

用于治疗慢性再障的主要手段是（）

A.脾切除术

B.糖皮质激素

C.右旋糖酐铁注射

D.雄激素

E.止血药物