Two inequalities are known to be true: B > C and E ≥ F. On their own they say nothing about B and F. Which single additional statement would make the conclusion B > F definitely follow?

To reach B > F the links must form one unbroken descending run from B to F. B > C already covers B to C, and E ≥ F covers E to F, so the missing piece must run downward from C to E. 'C ≥ E' supplies it: B > C ≥ E ≥ F, and since the run contains the strict link B > C, the composite is strict, giving B > F. Each of the others points the wrong way and leaves B and F unconnected. 'E ≥ C' places E above C, so the run from B breaks at C and F could be anything. 'F ≥ C' likewise attaches F above C rather than below it. 'C < F' puts C below F, which if anything argues for B being small relative to F, and certainly cannot force B > F.