Got the question right in like 10 seconds but I got blind reviewed so I second guessed myself and BR'ed a wrong answer... whoopsie

#feedback the chart for answer choice C is incorrect, the conclusion should be classroom → /laboratory

@aviemann In that case that would rule out the "exactly half" option, since if it is not the case that most A are B, then that could mean there is an equal amount of A and B.

@MargaretKing

Flipping them as you did changes the meaning and does not follow, as in next room → /see him is not the same as /see arun -> in the next room. All we know from the question is that if he is in the next room, we do not see him. But if we do not see him, we do not necessarily know if he is in the next room or not. Not seeing Arun is a necessary condition for him being in the next room, meaning that he can be in the next room, but it is not a sufficient condition for him being in the next room, as we cannot say for sure if we do not see him that he is in the next room. However, if we know that he is in the next room, then we can say with 100% certainty that we do not see him, meaning that him being in the next room is a sufficient condition for his not being seen.

Same applies with the contrapositive flip "see him -> /(in next room)". Seeing him is a sufficient condition to know that he is not in the next room, but if all we know is that he is not in the next room, we cannot say for sure if we see him or not, as he could be somewhere else entirely. Seeing him is sufficient for knowing he is not in the next room, and his not being in the next room is necessary to see him, but not sufficient.