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Critical reasoning: what must be true

VerbalCritical reasoningEasy

By Devin Marsh, editorPublished 1 March 2026Last checked 31 July 2026

This item was written for this site and solved a second time from scratch before it went up, so that exactly one answer survives. The byline is a masthead name, explained in full on who writes this, and the sourcing rules are set out on the standards page.

All engineers at Firm X work remotely. Some engineers at Firm X are project managers. If the statements above are true, which of the following must also be true?

  • AAll project managers at Firm X are engineers.
  • BSome project managers at Firm X work remotely.
  • CMost engineers at Firm X are project managers.
  • DAll remote workers at Firm X are engineers.
  • ESome engineers at Firm X do not work remotely.

Try it before you scroll. Two minutes on the clock, then commit to an answer.

Correct answer: B

Chain the two statements. Some engineers are project managers, and every engineer works remotely. So those project managers who are engineers inherit the remote property: some project managers work remotely. That is (B).

A quick set picture helps: Engineers is a circle entirely inside Remote workers. Project managers overlaps the Engineers circle (that is what “some engineers are project managers” says). Any overlap with Engineers is automatically inside Remote, so PM ∩ Remote is nonempty.

Why the rest fail:

  • (A) reverses the overlap. Some engineers being project managers does not mean all project managers are engineers; the firm may employ non-engineer project managers.
  • (C) upgrades “some” to “most,” which the premises never support.
  • (D) reverses the first statement. All engineers work remotely, but other roles (designers, accountants) might work remotely too.
  • (E) flatly contradicts the first statement, which says all engineers work remotely.

On must-be-true questions, the correct answer is usually weaker and smaller than the traps. “Some project managers work remotely” commits to very little, which is exactly why it is guaranteed.

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