Not only did the systematic clearing of forests in the United States create farmland (especially in the Northeast) and gave consumers relatively inexpensive houses and furniture, but it also caused erosion and very quickly deforested whole regions.

1. Not only did the systematic clearing of forests in the United States create farmland (especially in the Northeast) and gave consumers relatively inexpensive houses and furniture, but it also
2. Not only did the systematic clearing of forests in the United States create farmland (especially in the Northeast), which gave consumers relatively inexpensive houses and furniture, but also
3. The systematic clearing of forests in the United States, creating farmland (especially in the Northeast) and giving consumers relatively inexpensive houses and furniture, but also
4. The systematic clearing of forests in the United States created farmland (especially in the Northeast) and gave consumers relatively inexpensive houses and furniture, but it also
5. The systematic clearing of forests in the United States not only created farmland (especially in the Northeast), giving consumers relatively inexpensive houses and furniture, but it

我觉的D不错,B似互前后不对称(前半句倒装,并且not only后有主语;但

后半句没倒装,并且but also后没主语)且which修饰的对象不大好,应该修

饰clearing吧.

引用一800分牛人的话:

I think the best choice is D. The first clause says that the

systematic clearing did some good things (created farmland and

provided inexpensive houses and furniture); the second clause

says that it also did some bad things (caused erosion and

deforested whole regions). "Not also" generally calls for a later

"but also," but "but also" does not necessarily call for an

earlier "not only." Example:

Rio de Janeiro has some of the world's most famous beaches, but

it also has some of the world's most notorious slums.

B:but also后面省略了主语systematic clearing,但是平行结构意思是和前面并列的：不仅。。而且。。。；which的指代有歧义不知是systematic clearing还是farmland.

D:but it also句意和前面转折，不用平行

相比之下，D的意思才是作者要表达的

i see, thanks!