What happens to R1 when obstructed by F4 while advancing toward second base?

In the scenario where R1 is obstructed by F4 while advancing toward second base, the correct outcome aligns with the rules governing interference and obstruction in baseball. When a runner is obstructed, the key principle is that the obstruction interferes with the runner's ability to advance safely. If the umpire determines that the obstruction directly affected R1's ability to progress to second base, they will declare R1 out as a penalty for the interference.

This ruling underscores the responsibility of fielders to manage their positions without impeding the progress of the runner. If a fielder, in this case, F4, obstructs a runner who is in the act of advancing, the runner is penalized due to the actions of the fielder, which disrupts the flow of the game's events and the runner's right to advance on the base paths.

There are other outcomes that could apply in different situations, such as calling R1 back to first base or allowing them to proceed safely if the obstruction did not affect their advancement. However, in this instance, since misconduct from F4 is clearly established, it leads to declaring R1 out.