Two inequalities are known to be true: M > N and P = Q. Which single additional statement would make the conclusion M > Q definitely follow?

The conclusion needs an unbroken descending run from M to Q. M > N covers the start and P = Q means anything established about P transfers to Q, so the missing piece must run downward from N to P. 'N ≥ P' supplies exactly that: M > N ≥ P = Q, and the strict link M > N makes the composite strict, giving M > Q. The other three all place P or Q above N and so break the run. 'P ≥ N' puts P at or above N, after which M > N says nothing about how M compares with P. 'Q > N' does the same through Q directly. 'N ≤ Q' also puts Q above N, which if anything pushes Q up and away from the required conclusion.