LSAT Inference Practice Question: Most-Plus-All Chain
An original inference question from our free Question of the Day rotation, built around a trap the LSAT reuses constantly: most-plus-all chain. Try it first, then read the explanation — it teaches the move, not just the answer.
Your job:Find what the statements force to be true.
Most of the stalls at the Saltwick harbor market sell seafood. Every stall at the market that sells seafood opens before seven in the morning. Some stalls at the market sell only crafts.
Which one of the following must be true, based on the statements above?
Show the answer & full explanation
The correct answer is E
The JBDM line
Just because all the seafood stalls open early doesn't mean all the stalls do.
The maybes
- MaybeMaybe every craft stall opens at nine — the conclusion survives.
- MaybeMaybe a hundred non-seafood stalls also open early — 'most' still holds either way.
Why E is right
Chain 'most' through 'all': most stalls sell seafood, and every seafood stall opens before seven. So most stalls open before seven — the majority is carried through intact. That's the one combination the facts force.
Why the others are wrong
- AThe craft-only stalls might open at noon; 'every stall' overreaches.
- BNothing stops a craft stall from opening early too.
- CThis reverses the rule. Every seafood stall opens early, but that doesn't make every early opener a seafood stall — a craft-only stall could open at six without breaking any fact.
- D'Some sell only crafts' doesn't force any stall to sell both.
Sammy's note
'Most' plus 'all' chains into 'most.' 'Some' plus 'some' chains into nothing.
What's a JBDM line?
Just Because Doesn't Mean (JBDM) is the Burton Method's foundational framework for attacking LSAT arguments: identify the premise, identify the conclusion, then say "just because [premise] doesn't mean [conclusion]" and generate "maybes" — alternative explanations that expose the gap between them. That gap is what weaken, flaw, strengthen, and assumption questions all test, so every explanation on this page starts with the JBDM line. It's a micro-lesson in the system, not just an answer key.
One question a day builds the habit
Answer today's question and start a streak — then see how Sammy teaches the whole system, JBDM included, in a free lesson.