Can someone try to explain question #61 in phase two of Illinois High School assc.umpire test. It read...

61. An illegal substitute bats and scores, but B4 is thrown out for the third out attempting to advance to second base. Even though a pitch has not been thrown, the run scores since both teams changed positions.

After reading it over ten times, was was still not sure of the question. I knew the answer had to be true or false. I flipped a coin and false won.

I don't know about IHSA, but this is what I have for ASA:

The illegal substitute was obviously not discovered prior to a pitch to the next batter, therefore all play would stand. If discovered anytime after that, a legal substitute would simply replace her on the base. Once she scores, there is nothing to be done other than disqualifying the illegal sub. Run counts.