Sentence Correction (SC) | Re: Not only did the systematic clearing of forests in the United States

GmatTutorKnight

Thanks for your response. Is there any OG qsn where using such a pronoun after 'but' was wrong.

I am wondering because if I consider a sentence: '' I have not only mastered CSS, but I have also learned HTML.

here 'mastered' is parallel with ''learned'' but we have ''I have'' in b/w ''BUT'' and 'ALSO'. Is this a wrongstructure.