What is the outcome if R1 misses second base after a fly ball is caught and the ball becomes dead?

The correct answer highlights the rule regarding a runner's obligation to legally touch the bases after a fly ball is caught, especially in a situation where the ball is dead. When R1 misses second base, the runner has committed a base running infraction. Since R1 cannot legally return to the base that was missed (in this case, second base) after the ball becomes dead, this means that the runner cannot advance safely and must face the consequences of their actions.

In this scenario, the player is considered to have lost the right to the base they missed, which is why they cannot return. The other options suggest outcomes that would not comply with standard baseball rules regarding missed bases and dead balls. For instance, saying R1 is automatically safe at third ignores the requirement of properly touching each base. Similarly, notions of being able to return to first base or needing to be tagged to be out misinterpret the consequences of missing a base on a caught fly ball under these specific circumstances. Thus, the focus on R1's inability to return to the missed base accurately reflects the rules and rationale governing base running in such a situation.