滑石的主成分是（）

A.硫

B.含水硫酸钙

C.二硫化二砷

D.硫化汞

E.水合硅酸镁

Jane will have to _____ her piano practice a long  time  if she wants to be a professional concert

performer.[ ]

A. set up

B. add up

C. keep up  

D. hold up