Introduction
Every sentence on the SAT Reading and Writing section must have a working predicate — a finite verb that is grammatically complete and capable of standing as the sentence's main verb. Questions in this subtopic ask you to choose the verb form that gives the sentence a real predicate, rescuing it from fragment status. These questions appear in the Standard English Conventions domain, which accounts for roughly 26% of operational questions in the Reading and Writing section.
The key challenge here is not exotic grammar — it is recognizing that -ing forms (present participles / gerunds) and to-infinitives are non-finite, meaning they cannot anchor a sentence on their own, no matter how long and impressive everything around them looks.
Core Concept
What is a finite verb?
A finite verb is one that is anchored to a subject and a tense. It changes form to show agreement and time, and it can stand alone as a sentence's predicate.
| Form | Example | Finite? | Why |
|---|---|---|---|
| Simple present | she runs | ✅ Yes | Marked for tense and person |
| Simple past | they discovered | ✅ Yes | Marked for tense |
| Present perfect | has revealed | ✅ Yes | Auxiliary + past participle = complete |
| Modal + base | can explain | ✅ Yes | Modal anchors it to tense |
| -ing form alone | running, discovering | ❌ No | No tense, no subject agreement |
| to-infinitive | to run, to discover | ❌ No | Signals purpose/noun role, not predicate |
Why -ing and to-forms fail as main verbs
An -ing form used without an auxiliary (like is, was, has been) is a present participle or a gerund (noun function). It cannot express when something happens or agree with a subject. A sentence like The team's decade-long effort to map the ocean floor revealing unexpected geological formations. has no main verb — revealing is dangling without a helper.
A to-infinitive (to reveal, to map) expresses purpose, desire, or a noun-like idea. It cannot serve as a predicate: The researchers to publish their findings next spring. is a fragment.
Why long noun-phrase openings are dangerous
SAT passages often place an elaborate noun phrase before the verb slot. The longer that phrase is, the easier it is to mistake a participle inside it for the main verb. Consider:
The committee's ambitious plan, drafted over three years and involving experts from twelve countries, representing a major shift in policy.
Students see representing and think the sentence is complete. It is not. The sentence needs a finite verb after the noun phrase: …represents a major shift or …represented a major shift.
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