This one is one of my all-time favorites, partly because
sloths are kind of awesome. Plus, it’s a good illustration of something we discussed in
this YouTube video (which, sadly, does not contain any sloths): if you don’t notice the tasty stuff in the non-underlined portions of the sentence, you might waste a ton of time on this question.
With that in mind...
Quote:
(A) sloths hang from trees by long rubbery limbs and sleep fifteen hours a day, moving infrequently enough
This sounds great. But it’s wrong.
Hopefully, you noticed the word “its” at the end of the sentence. That means that “sloth” needs to be singular. So (A) is spectacularly wrong because of the non-underlined pronouns buried at the end of the sentence.
Quote:
(B) sloths hang from trees by long rubbery limbs, they sleep fifteen hours a day, and with such infrequent movements
(B) has exactly the same error as (A): “its toes” and “its coat” need to refer to a singular sloth, and (B) only gives us the plural “sloths.”
The parallelism is also pretty wackball in (B). (And no, “wackball” isn’t a word. But it should be.) We have: “…sloths
hang from trees by long rubbery limbs,
they sleep fifteen hours a day, and
with such infrequent movements…” So we have a verb (“hang”), a noun with a verb (“they sleep"), and a weird prepositional phrase (“with such infrequent movements…”). That’s very much not parallel.
So (B) is out.
Quote:
(C) sloths use their long rubbery limbs to hang from trees, sleep fifteen hours a day, and move so infrequently
The parallelism is defensible in (C). Sloths use their limbs to do three things: “hang from trees”, “sleep 15 hours a day” (I'm totally jealous!!), and “move so infrequently…”. Not bad.
Trouble is, “its coat” and “its toes” still require a singular referent, and “sloths” is plural in (C). So (C) can be eliminated.
Let’s compare our last two options side-by-side:
Quote:
(D) the sloth hangs from trees by its long rubbery limbs, sleeping fifteen hours a day and moving so infrequently
(E) the sloth hangs from trees by its long rubbery limbs, sleeps fifteen hours a day, and it moves infrequently enough
“Sloth” is singular in both, so the pronouns are cool now. That’s nice.
So then the only real difference is the parallelism. In (E), we have “the sloth
hangs from trees…,
sleeps 15 hours a day, and
it moves…” Nope, that’s wrong: we have a verb, a verb, and then a noun and a verb. That’s not parallel.
But what about (D)? People like to tell me that it’s not parallel, either. But (D) is structured differently than (E): it’s a nice clause (“the sloth hangs from trees…”), followed by two parallel “-ing” modifiers (“sleeping” and “moving”). That’s great: “sleeping 15 hours a day” and “moving infrequently” both make perfect sense as modifiers for “the sloth hangs from trees”, since both of those “-ing” words tell us more about what happens when the sloth hangs from trees.
So (D) might not SOUND parallel, but it is. And it’s the best answer.