Approved April 24, 1800, the act of Congress that made provision for the removal of the government of the United States to the new federal city, Washington, D.C., also established the Library of Congress.

A. Approved April 24, 1800, the act of Congress that made provision for the removal of the government of the United States to the new federal city, Washington, D.C., also established
B. The act of Congress, which was approved April 24, 1800, making provision for the removal of the government of the United States to the new federal city, Washington, D.C., also established
C. The act of Congress approved April 24, 1800, which made provision for the removal of the government of the United States to the new federal city, Washington, D.C., and established
D. Approved April 24, 1800, making provision for the removal of the government of the United States to the new federal city, Washington, D.C., the act of Congress also established
E. Approved April 24, 1800, the act of Congress made provision for the removal of the government of the United States to the new federal city, Washington, D.C., also establishing


I chose E, the supposed OA is A.

A = the act of Congress that made ...., also established <--- not an indepednet claushe, WRONG!!

anyone?

that is, indeed, an independent clause. the problem is that it's a very long independent clause - the 'middleman' itself is longer than most actual sentences. that's a doozy.

remember that you should either condense or eliminate these interloping constructions (modifiers, prepositional phrases, and the like) so that you can better understand the structure of the sentence. if you do that here, you get the following:
the act that did X ... also did Y
that's an independent clause.

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the big problem with choice e is that it strips 'the act of congress' of a necessary modifier - so that, instead of saying 'the act of congress that did blah blah blah', it just says 'the act of congress' - as if congress has only ever performed one act in its history. that's an unacceptable (and absurd) change in meaning.