I always have so many things to__________when I come back to the company after a trip abroad. [ ]

A. add to  

B. contribute to

C. attend to  

D. appeal to

下列成分有可能与大分子抗原结合而出现肉眼可见反应的是（）。

A.IgG的H链

B.IgG的L链

C.Fc段

D.F（ab＇）₂段

E.Fab段