The blue jeans _______ 50 dollars. And that black pair of jeans _______ 60 dollars.

A．are; costs

B．are; cost

C．pay; are

D．spend; is

检查某药物中的砷盐，称取样品2.0g，依法检查，与标准砷溶液2.0ml(1ugAs/ml)在相同条件下制成的砷斑比较，不得更深。砷盐的限量是( )

A．百万分之一

B．百万分之二

C．百万分之十

D．0.01%

E．0.1%