UPDATE: You can find this blog and others about idioms in our new GMAT Idiom eBook!
First, a practice GMAT Sentence Correction question:
1) Because of Elnath Industries posting a second consecutive quarter of losses, its stocks tumbled 20% in the last three days.
(A) Because of Elnath Industries posting
(B) Because of Elnath Industries having posted
(C) Because Elnath Industries posting
(D) Because Elnath Industries posted
(E) Because Elnath Industries had been posting
By itself, the word “because” is a subordinate conjunction. What does that mean? It means, this word opens a subordinate clause. A subordinate clause, like any clause, must have a complete [noun] + [verb] structure within it, like a mini-sentence: in fact, if you drop the subordinate conjunction, the rest of the subordinate clause should be able to stand alone as a sentence. Furthermore, the fact that this clause is subordinate (i.e. dependent) means there must be another main, independent clause providing the meat-and-potatoes of the sentence.
The general outline of a sentence involving the word “because” might be:
“Because” + [sub. noun] + [sub. verb], [main noun] + [main verb].
Of course, all kinds of adjectives, adverbs, and other modifies can be added to this structure. The [sub. noun] + [sub. verb] provide the structure of the subordinate clause — and could stand on their own as a complete sentence. The sentence as a whole depends on the [main noun] + [main verb] as its core structure. For example,
2) Because teenagers are insatiably hungry, their parents are always buying food.
Notice that the [noun] + [verb] within the subordinate clause, “teenagers are insatiably hungry”, could work as its own sentence: that’s a great trick to test a clause on the GMAT Sentence Correction. Nevertheless, in this context, “their parents” is the main subject and “are … buying” is the main verb.
The words “because of” are a compound preposition. Prepositions are designed to be followed by only a noun —- “because of the rain“, “because of the parade“, “because of the child’s temper tantrum“, etc. The object of this or any preposition can be a gerund or gerund phrase —- “because of waiting for the senator“, “because of limited parking“, “because of having eaten out every night this week“, etc. That last example is getting to the limit of how much action, how much story, the GMAT likes to pack inside a prepositional phrase. On the Sentence Correction, the GMAT finds the following structure problematic:
when this structure contains an “action word” participle. Even though this could be grammatically correct in a technical sense, many would be likely to find this in poor taste, and for GMAT Sentence Correction purposes, this is 100% wrong.
Example “Because of the President going to Myanmar …” = WRONG!
As far as the GMAT is concerned, this is just too much action, too much story, for a preposition to handle. If you are going to have both an action and the person/agent performing the action, then what you need is a clause, not merely a prepositional phrase.
Having read this post, take another look at the practice sentence above before reading the explanation below. Here’s another practice Sentence Correction question involving this idiom:
Practice question explanation
1) We have an actor & an action, so a preposition is not enough: we need a full [noun] + [verb] clause, which means we need the subordinate conjunction “because”. The first two, with the preposition “because of”, are wrong. Choice (C) involves the missing verb mistake — having a [noun] + [participle] in place of [noun] + [verb]. Only (D) & (E) have “because” + [noun] + [verb]. Choice (E) involves a very strange tense: the past perfect progressive — this is not at all required by or appropriate to the context. Thus, the only possible correct answer is (D).