--Beijing is really an old city and there're many places of interest.

--So it is. Why not stay here for        two days?

A. other

B. others

C. another

亲和板结合分离法中，间接法包被于塑料平皿或细胞培养板的抗体是（）

A.CD20mAb

B.CD2mAb

C.兔抗人Ig抗体

D.CD19mAb

E.兔抗鼠IgG抗体