During the play where R3 touches home plate, what is the ruling about B4 if he does not reach first base?

In this scenario, if R3 touches home plate, the play situation reflects the completion of a run. The critical aspect to consider is whether B4's failure to reach first base impacts R3's run. In baseball, a run counts when a runner legally touches all bases in order and reaches home plate before any outs are made concerning that play.

If R3 has safely touched home plate, his run is valid regardless of whether B4, still at bat, reaches first base or not. The status of B4 does not negate the fact that R3 has scored, assuming no interference or rule violation occurred that involved R3's run. Thus, as long as R3 legally touched home plate, his run counts.

The play continues concerning B4, but the critical outcome here is extracting that R3's run is entirely separate and stands as valid, confirming that the run counts for R3. The other options would not appropriately apply to this situation since R3’s status is independent of B4's actions in this context.