as these little cars can go only 65 kilometres per hour .If big cars are still used along with the s

题目

as these little cars can go only 65 kilometres per hour .If big cars are still used along with the small __7__ ,two sets of road will be __8__ in the future .
7.A.one B.ones C.seat D.seats
8.A.need B.needing C.needs D.needed
这两个空选择B和D请问为什么这第一个空选择B呢?

答案

7 因为 前面 cars 表示复数 one的复数是 ones (ones 代替 cars)
8 will be done 作为将来完成时的 被动语态,因为后面是 in the future,所以是将来完成时