在FeSO4和Fe2(SO4)3的混合物中,氧元素的质量分数为a%,则该混合物中铁元素的质量分数为( )
A:2a%
B:1﹣a%
C:1﹣0.5a%
D:1﹣1.5a%
teachers, you, new, have, do (?) (连词成句)
____
— No, it isn't. I think it's _______.