Independent clauses: what actually joins two sentences
An independent clause is a group of words that could stand alone as its own sentence. It has a subject, a verb, and a complete thought. Most boundary questions on the SAT come down to one question: can two clauses sit next to each other exactly like this, or does something between them need to change?
There are only a few ways to join two independent clauses correctly. A period keeps them fully separate. A semicolon links them without a conjunction. A comma works only when it is paired with a coordinating conjunction: and, but, or, so, for, nor, yet. Drop the conjunction and keep just the comma, and you get a comma splice, which the SAT tests constantly.
Take this pair: "The module timer hit zero, Maria still had three questions left." That comma alone cannot hold two full sentences together. Fixed, it could read "The module timer hit zero. Maria still had three questions left." or "The module timer hit zero, and Maria still had three questions left." Same information. A boundary that actually works.
While repairing a seawall in ______ engineers uncovered the timber frame of a fishing boat that had been buried in the fill.
Which choice completes the text so that it conforms to the conventions of Standard English?
Fragments: when a clause only looks like a sentence
A fragment happens when a group of words gets punctuated like a full sentence but cannot stand alone. The classic trap on the SAT is a dependent clause dressed up with a capital letter and a period. Words like because and which turn a clause dependent, so it needs to attach to something else.
"Because the second module was harder." is not a sentence by itself. It is a piece of one, waiting for the rest: "Because the second module was harder, her score climbed more than she expected." Relative clauses starting with which or who cause the same problem when they get cut loose from the noun they describe.
Extra information gets set off from the rest of a sentence with matching punctuation on both sides: two commas, two parentheses, or a pair of dashes.
Punctuation inside a sentence: commas, colons, and paired marks
Extra information gets set off from the rest of a sentence with matching punctuation on both sides: two commas, two parentheses, or a pair of dashes. Pick one style and stick with it for that sentence. Mixing a comma on one side with a dash on the other is exactly the kind of small slip these questions are built to catch.
A colon works the same way every time: what comes before it has to be a complete sentence on its own. "She brought exactly what she needed" can stand alone, so a colon can follow it. "She brought" cannot stand alone, so a colon should not follow just that. Whatever comes after the colon, a list, one item, or a full explanation, does not change the rule.
Subject-verb agreement: what hides between the two
Subject-verb agreement questions usually put real distance between the subject and the verb on purpose. Whatever sits in between is the distraction, so find the actual subject and ignore it. "The list of instructions for the essay section (is/are) posted at the front of the room." The subject is list, which is singular, so the verb has to be is, no matter how many nouns show up in the phrase in front of it.
Two other patterns come up constantly. Collective nouns like team or committee normally take a singular verb, since the group is acting as one unit. Sentences that flip the usual order, starting with there or here, hide the subject after the verb: "There (is/are) two ways to solve this." Skip ahead to find the real subject: two ways. Match the verb to that, not to there.
A fast way to check your answer under time pressure
When you are not sure, read the sentence back with only the two clauses in it and drop everything else. If two full sentences are left standing next to each other with just a comma between them, that is a comma splice, whatever else the sentence seemed to be doing. If half of what is left cannot stand on its own, you are looking at a fragment instead.
Reading the sentence at normal speed, in your head, catches a surprising number of these on its own, since a fragment usually sounds unfinished even before you can name the rule it breaks. If the same few rules keep costing you points on practice sets, StudyPebble's practice by skill mode walks through explanations for punctuation and agreement questions on their own, instead of mixing them in with everything else.
Already have a stack of missed Conventions questions from a Bluebook test? Uploading them at /mistakes/upload sorts your misses by the exact rule behind each one, so you know which of these to go back and drill first.