How does emphasizing the changes have taken place in america strengthen lincoln's argument?

Lincoln's argument was against slavery expansion in the country. Also, through his philosophy, we can see a democratic vision, because Lincoln was able to express people's feeling and thoughts, that's why he was supported even being an ''unknown politician''. People saw in him something different and sincere, due to his acts. A man of his word, we can say.

what is the question ?

the sentence that avoid faulty coordination is:

culture, which is well represented in philadelphia, plays a major role including theatre, music, and the visual arts.  

faulty coordination occurs when the writer gives equal importance two different ideas (clauses) which in fact are not equivalent. in order to correct a misplaced clause or idea, the writer can place less important or emphatic ideas in a relative clause as in the previous sentence.