可溶性纤维蛋白单体形成交联纤维蛋白的过程中，参与的凝血因子是（）

A.因子Ⅻ

B.因子Ⅻa

C.因子a、Ca²⁺

D.因子Ⅹ

E.因子Ⅹa、Ca²⁺

The number of articles published on smoking _______ amazing, but a great number of people _______

still smoking.[ ]

A. is; are      

B. is; is    

C. are; are  

D. are; is