高一英语问题7. The little boy still needs the _____ 20 dollars to

高一英语问题
7. The little boy still needs the _____ 20 dollars to do with some things _____.
A. remaining; remained to be settled
B. remaining; remaining to be settled
C. remained; remained to settle
D. remained; remaining to settle
答案为b，请解释
为什么前一空不是remained，不是被留下的