The state of California contains 58 counties, of which some of them ha

OFFICIAL SOLUTION

Here, we get clause construction as well as what is sometimes called a “subgroup modifier”.

The word “which” is a relative pronoun, and this means two important things. First, “which” begins a subordinate clause that, like any clause, must have a full [noun] + [verb] structure. Second, the pronoun “which” itself is the subject of this subordinate clause. Choices (B) & (E) run afoul of the first rule — they follow “which” with a participle and an infinitive respectively, not a full bonafide verb. Choice (A) has a bonafide verb, “have”, but it gets in trouble with the second rule — it has a double subject, the word “which” and the phrase “some of them” — this would be a like the sentence, “My sister she is smart” — the [noun] + [pronoun] structure is redundant and incorrect. Choice (A) makes exactly the same mistake. None of these three choices is correct.

The phrase “some of them” is a noun. If we follow a noun with a full verb “have”, as (D) does, this creates an independent clause —- everything after the comma could stand on its own as a complete sentence. Again, the problem is — we have [independent clause], [independent clause] — that’s the structure of a run-on sentence. Choice (D) makes this mistake and is not correct. Choice (C) follows the noun “some of them” with the participle “having” — this is the [noun] + [participle] structure of an absolute phrase. This is grammatically correct, and because there’s a grave problem with each of the other four answer choices, (C) is the only possible answer.