Mount Diablo, near San Francisco, CA, is not a very high peak, with an

Magoosh Official Explanation:

A question about Mount Diablo in northern California.

The prompt has one independent clause before the underlining, then the conjunction “but.” This implies that we need another independent clause after the word “but.”

Choice (A) is a mess. First of all, it begins with a “due to” mistake. Furthermore, there are absolutely no full verbs after the word “but,” so no independent clauses. Choice (A) is incorrect.

Choice (B) is grammatically correct but logically flawed. Before the underlining, we have the fact that Mt. Diablo is not very tall, then the strong contrast word “but.” We are expecting a contrast in the next independent clause. What does choice (B) give us? It’s adjacent to low flat land. Overall:

Mt. Diablo is not very tall but it’s adjacent to low flat land.

In that sentence, the word “but” is playing no useful role at all, because there’s no contrast between those two facts. It’s incorrect to use a strong contrast word when there’s no contrast! Choice (B) is incorrect.

Choice (C) is elegant and well organized.

Choice (D) repeats the logical problem of (B) and also has a pronoun problem. The pronoun “this” refers to the action of the previous clause. That’s a pronoun mistake: pronouns can refer only to nouns, not to the action of clauses. Choice (D) is incorrect.

Choice (E) has the following organization:

[ind. clause #1] “but” [prepositional phrase] “and” [ind. clause #2]

Grammatically, this is a train wreck. The conjunctions “but” and “and” are parallelism markers and need to link equivalent elements. We would need another independent clause between “but” and “and.” As is, choice (E) is incorrect.

The only possible choice is (C).