Terrible SAT Explanations

One of the ideas behind Kahn Academy was leveling the playing field. By making quality test prep materials available to everyone, students who have the money to pay for tutors and prep classes would no longer have an advantage. Unfortunately the explanations on Kahn Academy are sometimes so bad that they put the students who rely on it at a disadvantage.

Consider this question that was recently shared on reddit:

 

11.  A) NO CHANGE,
       B) field she
       C) field; she
       D) field: she

Personally, I think that either C or D should be acceptable. There are two independent clauses, and the second one elaborates on the first, so either a colon or a semicolon should be fine.

Kahn Academy insisted that only the semicolon is acceptable, but the reason it gives is flat out wrong.

"Walker was not only a trailblazer in the medical field" is not a relative clause. It is an independent clause that can stand alone as a sentence. It feels somewhat incomplete because it so clearly anticipates a discussion of the person's other accomplishments, but it is still an independent clause.

What it isn't is a relative clause, at least according to the Writing Center at the University of North Carolina (and every other source I could find):

A relative clause is one kind of dependent clause. It has a subject and verb, but can’t stand alone as a sentence. It is sometimes called an “adjective clause” because it functions like an adjective—it gives more information about a noun. A relative clause always begins with a “relative pronoun,” which substitutes for a noun, a noun phrase, or a pronoun when sentences are combined.

For example "who lives next door" is a relative clause in the sentence "I spoke to the woman who lives next door." It provides information about the woman. On the other hand, "Walker was not only a trailblazer in the medical field" contains no relative pronoun and it does not give information about any noun other than the one that appears in the clause.

I often think that there are much better ways to get to the right answer on a question than the one  given in the College Board's explanation. It is less frequent that I think that the College Board's explanation is objectively incorrect, but it happens enough that I don't think that test prep tutors  have to worry about being put out of business by Kahn Academy any time soon.