请教两个语法：

请教两个语法：

During early nineteenth-century Boston, the architect Charles, eager to make the city beautiful, sometimes provided free plans for people building homes.

答案给的是A 我觉得D也有问题应该是build houses吧

Only with early seventeenth-century observers did the music of the origial inhabitants of the United States and Canda entered recorded history.

答案给的是D，为什么D呢？是history前要加the还是？？为什么A不错呢？

另：nineteenth-century  和nineteenth century  有什么区别呢？？

恳请赐教谢谢先！！！

1、 during Boston 当然是错误的；

provide something for somebody
The hotel provides a shoe-cleaning service for guests.

for 后用building homes是不错的。

2、Only with early seventeenth-century observers did the music of the origial inhabitants of the United States and Canda entered recorded history.

原序应是： the music entered recorded history

状语only with ...observers提前，用倒装。

nineteenth-century  和nineteenth century  有什么区别呢？？

前者是形容词，后者应用the ,而前者倒不一定用the。

第一题介词应该是 in 指地点 Boston

第二题是由 Only with 代出的倒装句, did 后面用原型, 这绝对肯定的.