help on ASA test #45

[shipwreck]

Please help me on #45. R1 is on 1B with no outs, unreported substitute B2 is at bat with a one ball and a one strike count B2 grounds into a force out at 2B retiring R1. Before the next pitch, the defensive team notifies the unpire that B2 is unreported. The umpire should rule:
a: R1 is out. B2 is out, removed from 1B and is disqualified.
b: R1 is returned to 1B. B2 is removed from 1B and disqualified.
c: R1 is returned to 1B and a substitute enters to bat for B2.
d: R1 is out and a legal substitute replaces B2 at 1B

It seems to me they are all incorrect.
a:B2 would not be out so incorrect answer.
b:R1 was out on the play and the rules states that all outs that occur on this play will stand, so incorrect.
c:same for this question, R1 was out on this play, so incorrect.
d:rule states that all runners(including batter)will return to the base occupied on the batted ball(she was batting) so cannot be replaced at 1B, so incorrect.
PLEASE shed some light on this question? Thanks, Dave