关于几个语法问题

Queena_531

massachusetts was (first explored) in the late sixteenth and (early) seventeenth
(centuries),and the first pernament (settlement) at plymouth in l620
答案是d，为什么不把centuries改称单数呢，d怎么改呢？



hovercrafts,or air cushion vehicles. are unusual-----------taravl over land and water on a layer of air
a that they
b in that they
虽然b更好，但是a有什么语法错误么，为什么不能选a呢？


现在比较晕了，问个比较傻的问题 ，突然不太明白percent 和 percentage的区别了
给我讲讲吧，谢谢啦！

gre3333

1. because: there are many centuries in the late sixteenth and early seventeenth.

   d: --> settled     

2. 表示原因，用in that/ because

3. 建议查一下字典