What is the ruling if an infielder intentionally drops the ball after B2's line drive?

The ruling that B2 is out and R1 returns to first is correct because the infielder's intentional act of dropping the ball is classified as an appealing play. When a fielder intentionally drops a ball that is caught, they can create a situation where the baserunner's actions can be affected. According to NFHS rules, if an infielder drops a ball intentionally, it allows for the opportunity to claim the catch was made, thereby leading to B2 being called out.

The play is determined to be regarding B2's status; since the ball was intentionally dropped, it signifies that B2 is indeed out due to the nature of the play. Furthermore, R1’s obligation to return to first base is a result of that call, as the rules state that upon the interception or handling of the ball in a unique and intentional way, the advancing runner will revert to their previous base due to the out recorded.

This reasoning aligns with the Concept of the Infield Fly Rule and the general guidelines surrounding infield plays. The inclusion of the intentional act influences the outcome significantly, thereby rendering R1 unable to advance safely, and mandating they return to their original base.