Must Be True and Inference questions ask you to identify a conclusion that must be true given the premises stated in the stimulus. You accept every statement as fact and find what follows with certainty — not what seems likely or plausible.

A) The Core Rule

Treat everything stated in the stimulus as 100% true. Your job is not to evaluate whether the statements are believable — accept them and ask: what must follow from these facts?

B) Identifying the Question Type

• "Which of the following can be properly inferred…"
• "Which of the following must be true based on the above?"
• "The statements above, if true, best support which of the following?"
• "Which of the following conclusions can be drawn from the information above?"

C) Deductive Logic: Quantifiers

GMAT inference questions frequently involve statements with quantifiers. Master these inference rules:

• "All A are B" → any specific A is also B; some B are A (but not necessarily all B are A). You cannot reverse the direction.
• "Some A are B" → at least one A is B. You cannot infer "most" or "all." "Some" = "at least one."
• "No A are B" → zero overlap; equivalent to "all A are not B" and "all B are not A" (this one is reversible).
• Chain inference: "All A are B" + "All B are C" → "All A are C." Valid chain. But "All A are B" + "All C are B" does NOT let you conclude anything about A and C.
• Contrapositive: "If A then B" is logically equivalent to "If not-B then not-A." This reversal with negation is always valid. "If A then B" does NOT mean "If B then A" (that is a logical fallacy).

D) Logical Operators

• And: both conditions must be true for the combined statement to be true.
• Or: at least one condition is true (inclusive — both can be true simultaneously).
• If-then: "If P, then Q." P is sufficient for Q. Q is necessary for P. Contrapositive: "If not-Q, then not-P."
• Not: negating a conjunction ("not (A and B)") → "not-A or not-B." Negating a disjunction ("not (A or B)") → "not-A and not-B."

E) What Correct Answers Look Like

• A paraphrase of one or more statements from the stimulus.
• A logical combination using quantifier chaining or contrapositive reasoning.
• Cautious language: "at least some," "in some cases," "it is possible that" — these are safer and more likely correct than absolute claims.

F) The Five Trap Types

• Could Be True / Likely True: plausible but not certain. The bar is logical necessity, not probability.
• Too Extreme: absolute language ("always," "never," "all") when the stimulus only supports a weaker claim.
• New Information: introduces a concept or entity not present in the stimulus.
• Shell Game: uses terms from the stimulus but modifies the relationship subtly.
• Opposite: contradicts or reverses a relationship stated in the stimulus.

G) Strategy

1. Read the stimulus carefully. Note quantifiers (some, most, all, none) and conditional logic (if-then).
2. For conditional logic: identify which direction is valid (A→B does not mean B→A).
3. Pre-think: what logical combinations can you build from these statements?
4. For each answer choice: "Does the stimulus guarantee this, or merely allow it?"
5. Correct answers should feel like they add little new beyond what the stimulus already says.