Grammar Skill Drills — Boundaries
Sixteen items, four sub-skills, answer and reason immediately under each
9 min read
MERIDIAN™ · © 2026 · original practice items (not real SAT questions). Not affiliated with or endorsed by the College Board. SAT® is a trademark of the College Board.
How to use this. Blocked practice: one sub-skill at a time, four items each. Pick an answer and the reasoning appears immediately, naming the rule and the defect in each choice you did not pick — that immediacy is the point of this document, and it is why the answers are not at the back the way they are in the Practice Bank.
Score your FIRST answer on each item. You can retry as often as you like, and you should, because the aim is to end up knowing it rather than to be measured. But the gates below only mean something against the answer you gave before you were told.
The gate. Three of four on a sub-skill and you move to the next. Two or fewer and you go back to that rule in the Grammar Ruleset Vault before drilling it again. Do not push on with a leaky sub-skill; the mixed unit test will find it.
The conventions this drill follows (digital-SAT rules): a colon must follow a complete clause; a semicolon equals a period and joins two independent clauses; a supplement takes a matched pair of marks; no comma ever sits between a subject and its verb; singular they is acceptable for a generic person and is never marked as an error here.
The Boundary Test, which decides most of what follows. Cover the blank. Is what comes before it an independent clause? Is what comes after it an independent clause? Two independent clauses may be joined by a period, a semicolon, a comma + FANBOYS, a colon, or a dash — and never by a bare comma.
SUB-SKILL 1 · LINKING TWO CLAUSES
Check yourself
1. The observatory closed for renovations in 2019 ____ it reopened three years later with a mirror twice the original diameter.
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2. Because the river floods every spring ____ the villagers built their storehouses on stilts.
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3. The alloy is unusually light ____ it withstands temperatures that would warp structural steel.
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4. Ptolemy's model placed the Earth at the centre of the universe ____ nevertheless, it predicted planetary positions accurately for fourteen centuries.
SUB-SKILL 2 · PUNCTUATION MARKS
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5. The expedition packed only what two men could drag ____ dried fish, seal oil, and a single sledge.
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6. The panel included researchers from Lima, Peru ____ Nairobi, Kenya; and Oslo, Norway.
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7. The archive contains ____ letters, ledgers, and three unpublished manuscripts.
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8. She brought only one instrument on the voyage ____ a brass sextant her father had used at sea.
SUB-SKILL 3 · SUPPLEMENTS
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9. The composer ____ whose symphonies went unperformed in her lifetime ____ is now programmed on four continents.
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10. Marie Tharp's map of the ocean floor ____ published in 1977 after two decades of soundings ____ changed how geologists pictured the Earth.
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11. The physicist ____ Lise Meitner ____ was denied a share of the prize awarded for the discovery she had explained.
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12. Her second novel ____ The Waiting Room ____ sold fewer than four hundred copies in its first year.
SUB-SKILL 4 · COMMAS THAT MUST NOT BE THERE
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13. The long-abandoned lighthouse at the northern tip of the island ____ still appears on current nautical charts.
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14. The technician calibrated the spectrometer ____ and then recorded a full night of readings.
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15. Students ____ who submit their portfolios after Friday ____ will be considered only in the second round.
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16. The wildfire jumped the ridge shortly after midnight ____ forcing the evacuation of three valley towns before dawn.
SCORE YOURSELF
| Sub-skill | Items | Gate |
|---|---|---|
| Linking two clauses | 1–4 | 3 of 4 |
| Punctuation marks | 5–8 | 3 of 4 |
| Supplements | 9–12 | 3 of 4 |
| Commas that must not be there | 13–16 | 3 of 4 |
Any sub-skill below the gate: reread its rule in the Grammar Ruleset Vault, then take the matching block of the Grammar Practice Bank before you go on.
All four at gate: move to Skill Drills — Form, Structure & Sense.
REFERENCE CARD — BOUNDARIES
| Situation | What is allowed |
|---|---|
| IC ____ IC | period · semicolon · comma + FANBOYS · colon · dash |
| IC ____ IC, never | a bare comma (comma splice) or nothing (run-on) |
| Dependent clause first | comma after it |
| Conjunctive adverb (however, nevertheless, therefore) | semicolon before, comma after |
| Colon | complete clause before it; anything after it |
| Semicolon in a list | only when items contain internal commas |
| Supplement | matched pair — two commas, two dashes, never one of each |
| Essential information | no marks at all |
| Subject and its verb | never separated |
| Compound predicate | no comma before the second verb |
Up next
Grammar Skill Drills — Form, Structure & Sense
Twenty-four items, six sub-skills, answer and reason immediately under each
11 min