Interest is as ________ to learning as the ability to understand, even more so. [ ]

A. vital  

B. available

C. specific  

D. similar

某人的红细胞与B型血的血清凝集，而其血清与B型血的红细胞不凝集，此人血型为

A．A型

B．B型

C．O型

D．AB型

E．Rh型