First, a practice GMAT Sentence Correction question:
1) Extracting pure aluminum from bauxite and other ores using the Hall-Héroult process, with a vast amount of electrical energy separating the element from aluminum oxide, making aluminum an energy-dense resource with a huge carbon footprint.
- using the Hall-Héroult process, with a vast amount of electrical energy separating the element from aluminum oxide, making
- by means of the Hall-Héroult process, in which a vast amount of electrical energy separates the element from aluminum oxide, making
- by means of using the Hall-Héroult process, in which a vast amount of electrical energy separates the element from aluminum oxide, is making
- by means of the Hall-Héroult process, in which a vast amount of electrical energy separates the element from aluminum oxide, makes
- using the Hall-Héroult process, with a vast amount of electrical energy separating the element from aluminum oxide, makes
There are several –ing verb forms floating around with the aluminum --- what are they all doing? At the end of this post, I will discuss this question.
The –ing form of a verb is what we get when we stick an –ing at the end of the infinite form (i.e. the standard dictionary form) of a verb: talking, walking, singing, sleeping. If the infinitive form ends with a "silent e", we drop that to form the –ing form: writing, waking, loving, hoping. In some cases, a last letter is doubled: spinning, inferring, concurring, beginning. For the GMAT Sentence Correction, you need to know that the –ing can function as part of the verb, or as an adjective, or as a noun. That is to say, it can denote the progressive tense of a verb, or it can be a participle, or it can be a gerund. The GMAT will not ask you specifically about the names of these grammatical forms, but it's useful to know then so that you understand discussions of grammar. For the Sentence Correction, you don't need to know the names of the grammatical forms, but you definitely need to be able to distinguish what grammatical role the –ing form is playing in any sentence.
As a verb
The –ing form of a verb is used in the Progressive Tenses of a verb. For non-native speakers, the distinction between the simple present test ("I walk") and the present progressive test ("I am walking") is one of the most difficult to sort out. The Present Progressive Tense indicates action that is ongoing at the moment the speaker speaks about it:
2. Right now, I am reading this new book.
The Past Progressive indicates action that was happening at some very specific moment in the past, and/or exactly at the same time as some other event:
3. When you called last night, I was reading that new book.
In both of these, the –ing form "reading" is part of the main verb of the sentence. If the –ing form of the verb is immediately preceded by an auxiliary verb (is, are, was, were, have been, has been, had been, will be, etc.), that's a sure sign that the –ing is function as part of the verb, either the main verb of a sentence or the main verb of a subordinate clause. If no auxiliary verb immediately precedes the –ing form, then it must be playing one of the other roles.
As an adjective
The –ing from acts as an adjective, that is to say, a noun modifier, when it is a participle. The participle alone can modify a noun, or it can be followed by a direct object and/or by prepositions & adverbs, forming a participial phrase. Here's an example of a long participle phrase using a past participle.
4. The philosophy student, having read the complete works of Kant in German last semester, is going to read all of Hegel in the original this semester.
That entire phrase "having read the complete works of Kant in German last semester" is a participial phrase modifying the noun student. Because it acts as a noun, it is at least analogous to an adjective. This phrase would be an adjectival phrase. If the –ing form begins a phrase set off in commas, immediately following or preceding a noun, that's a sure sign that it's functioning as a participle. Participial phrase, though, like all noun modifiers, are not necessarily set off by commas. Whether or not to use commas depends on whether the modifier is vital. Here's a participial phrase acting as a vital modifier:
5. Copies of the book describing how to isolate weapons-grade plutonium in your kitchen were impounded and destroyed by federal agents.
The phrase "describing how to isolate weapons-grade plutonium in your kitchen" not only modifies the noun "book" but also make clear the identity of the book: that is precisely what makes it a vital noun-modifier, which is precisely why it is not separated from the rest of the sentence by commas. BTW, so far as I know, quite fortunately nobody actually would be able to isolate weapons-grade plutonium in an ordinary kitchen! It's slightly more difficult than making oatmeal cookies! J
As a noun
The –ing form of a verb can also act as a noun. In this case, it is a gerund. As a gerund, the –ing form of a verb acts as a noun and can play any of the "noun roles" in a sentence. Like a participle, a gerund can have its own direct object. For example
6. Reading is a time-honored means to self-edification, and for some, it is an end in and of itself.
7. The precocious child preferred reading literature to playing video games.
8. The idea of reading a good book under a warm blanket with a cup of hot cocoa makes a cold rainy day more palatable.
In sentence #6, the single gerund "reading" is the subject of the sentence. Notice that as a subject, a gerund is construed as singular. In #7, the gerund phrase "reading literature" is the direct object of the verb "preferred." Both the gerund phrase "playing video games" in #7 and the long gerund phrase "reading a good book under a warm blanket with a cup of hot cocoa" in #8 are objects of prepositional phrases. Anything a noun can do, a gerund can also do.
Here's another GMAT Sentence Correction in which an –ing verb form plays a role.
Having read this article, you may want to take another look at the practice question at the top before reading the solution below.
Practice question explanation
1) As the original sentence stands, to commits the "missing verb" mistake. The subject is the gerund phrase beginning with the gerund "extracting" has no verb in choices (A) & (B). Choices (C) & (D) & (E) provide a proper verb, although the present progressive "is making" in (C) is inappropriate --- there is no contextual reason to emphasize simultaneity. Only (D) & (E) contain the correct verb "makes".
The participial "using" is awkward because there is no explicit noun it modifies: in this context, the phrase "by means of" is far superior. BTW, the phrase "by means of using" in (C) is an abomination --- awkward, repetitive, and incorrect.
The prepositional phrase beginning with "with a vast amount…" is also awkward --- it is meant to describe an action, a process, that takes place within the Hall-Héroult process. A preposition such as "with" is not appropriate for describing an action contained within something else. We need a full subordinate clause, with its own subject + verb --- this is precisely what the construction "in which a vast amount…" supplies.
For all of these reasons, (D) is the strongest answer.
This post was written by Mike McGarry, GMAT expert at Magoosh, and originally posted here.