参与体液免疫应答的主要免疫细胞是（）

A.淋巴细胞

B.T细胞

C.B细胞

D.吞噬细胞

E.粒细胞

There are many factors contributing to the explosion of being too fat in the United States and the world,

______ the fundamental changes in the composition of their diet are first among them. [ ]

A. so

B. for

C. but

D. however