Obstruction question

[Rita C]

The Washington Officials Association has it's own test. I did well but missed one that I can't find casebook or rules directly addressing. (Or I may be missing it.)

Here's the question:

R1 is on third base, R2 is on 1st base, no outs. B4 hits a ground ball to F4, f4 trows the ball to F2 to prevent R1 from scoring. R1 gets into a rundown between 3rd base and home plate. During the rundown R1 is obstructed by F1. R1 is able to get back to 3rd base safely. During the rundown R2 had reached 3rd base. R2 is then tagged by f5 while standing on third base.

A. R2 is out.

B. The ball is dead as soon as the obstruction occurs.

C. Since R2 had reached 3rd base, R1 must be awarded home.

D. R1 is awarded the base she would have reached had the obstruction not occurred. Other runners are moved as....

(I don't have the last part of D.)

Rita