Gre mathematics
Choose A, there are 28 people in P who have never eaten. If all these 28 people have eaten in Q (that is, within 52 people), then the other 24 people must have eaten in P and Q, which is the least number. Because if less than 28 of the 52 people have not eaten at P, that is to say, more than 24 people have eaten at both P and Q..