Read the passage from the opinion of the court in Dred Scott v. Sandford, written by Justice Taney. The question before us is, whether the class of persons described in the plea in abatement compose a portion of this people, and are constituent members of this sovereignty? We think they are not, and that they are not included, and were not intended to be included, under the word "citizens" in the Constitution, and can therefore claim none of the rights and privileges which that instrument provides for and secures to citizens of the United States. On the contrary, they were at that time considered as a subordinate and inferior class of beings, who had been subjugated by the dominant race, and, whether emancipated or not, yet remained subject to their authority, and had no rights or privileges but such as those who held the power and the Government might choose to grant them.

Which statement best describes the fallacy in this passage?

Justice Taney assumes that the writers of the Constitution would agree with him about citizenship.
Justice Taney uses the argument that African Americans are not citizens to prove that they are not citizens.
Justice Taney assumes that the other justices on the court would agree with him about citizenship.
Justice Taney uses the argument that Dred Scott is an enslaved person to prove that he is not a citizen.

D. But see below. It could also be B.

Explanation:

The question is much more complicated than you might first think. The first knotty problem has to do with the term in abatement. This term actually means the right to sue in any court in the United States. Taney is arguing that African Americans do not have that right.

Then comes the  argument "Why not?" The reason he cannot sue is because he is not a citizen and that's where the rest of the argument comes in.  I think strange as it may seem, Taney uses the fact that they are not citizens to deny them the rights of citizenship.

He states plainly enough that those writing the constitution never intended African Americans to be citizens. They were conquered by a more powerful race. The fact of the matter, what happened in Pennsylvania when the constitution was written was much, much more complicated. The North wanted them to be included in the Constitution, the South would never permit it. The writing of the constitution is much more complicated than the simple assertion of what the Founding Fathers intended.

This case is considered by many to be one of the darkest stains on the Supreme Court baring no other case. Come to think of it, I suppose B and D are both correct. I think you are intended to choose D, but my own opinion is that it is B.

faulty parallelism is a grammar construction where there is no balance in the parts of a sentence they have a similar meaning but the grammar structure is not equivalent.

the correct version of this faulty parallelism in the sentence is:

jefferson wrote the declaration of independence, and he was the nation's third president.

the problem with the first version is that the sentence:

"jefferson was both the writer of the declaration of independence"

presents jefferson as both a subject and an agent for the verb "write" because if he was "the writer" then the declaration of independence was written by him, besides that fact, the sentence presents a dependent clause.

while the second sentence:

he was the nation's third president.

presents a basic subject+verb+object structure

so, to give a proper balance to the structure, or better said, to give a parallel structure, we must write a basic s+v+o structure in both sentences:

jefferson wrote the declaration of independence, and he was the nation third president.