Once you can name the rule a question is testing, you know exactly which tool to grab and which trap to watch for. Run every grammar question through a quick diagnostic — what changes across the four choices? — and the rest is mechanical.
| What changes in the choices | The rule | Your first move |
|---|---|---|
| A verb (is vs. are, runs vs. run) | Subject-verb agreement | Find the one true subject. |
| A pronoun (its vs. their, he vs. they) | Pronoun agreement / ambiguity | Find the one true antecedent. |
| Long intro phrase + comma | Dangling modifier | Run the "who/what" test. |
| A list or comparison | Parallel structure | Check the "dress code" of the items. |
| Only the punctuation | Sentence boundaries | Hunt for the comma splice. |
Subject-verb agreement: find the one true subject
The rule itself is from elementary school — singular subjects take singular verbs. So why does it cost so many points? Because the test hides the subject and verb from each other under a pile of distracting words. Think of the subject and verb as two socks that need to match, and the test's whole job is to dump a load of laundry — prepositional phrases, "by the way" clauses — on top of them.
"The box of old glass ornaments from my grandmother's attic ______ on the shelf." Your ear hears "ornaments" right before the blank and screams "sit." Your ear is wrong. Tidy the sentence up — cross out "of old glass ornaments" and "from my grandmother's attic" — and the subject is "box," singular, so it "sits." A few extra cases to know: with "neither/nor" and "either/or," the verb matches whichever subject is closest to it. And the sneaky singulars — collective nouns (team, family, committee) and indefinite pronouns (each, every, everyone) — are always singular, no matter how many people they seem to describe.
Pronouns: agreement and the ambiguity trap
A pronoun is a stunt double for a noun, and it has to match the noun it replaces in number. A singular company takes "its," not "their" — that mismatch is the most common version. The subtler trap is ambiguity. "The policy was announced to the department head. When they spoke, he seemed pleased." Who is "he" — the announcer or the head? When a pronoun could point at more than one noun, the fix is to replace it with the specific noun. Watch the its/it's and their/they're swaps too; "it's" is always "it is," never possessive.
Modifiers: the lost tourist
A modifier has to sit next to the thing it describes. The classic error is the dangling modifier, where the thing being described isn't even in the sentence. "After hiking for hours, the summit was finally in sight" literally says the summit went hiking. Run the who/what test on any opening phrase: ask "who hiked?" — the hikers — and make sure the word right after the comma is "the hikers." If it isn't, that's your error.
Parallel structure: same dress code
Items in a list or comparison have to wear the same grammatical outfit. "The consultant recommended hiring new staff, to invest in technology, and that we overhaul marketing" mixes three different forms; fix it to "hiring… investing… overhauling." A couple of specific structures the test loves: with "not only… but also," whatever follows "not only" has to match whatever follows "but also." And comparisons have to compare like things — "the marketing team's presentations were more compelling than the sales department" wrongly compares presentations to a department; it should be "than those of the sales department."
None of these reward instinct. They reward a fast diagnosis and the right tool, which is exactly why they're some of the most recoverable points on the test once you drill them. Forge can show you whether grammar is a steady strength or a quiet leak, and which specific rule keeps catching you, so your practice goes to the one that's actually costing you points instead of all of them at once.