Empty box. Randomly take two balls out of the bag at a time, put one ball into box A, if the ball is red, put the other ball into box B, otherwise put it into box C, and repeat the above process until all the balls in the bag are put into the box, and then ().

A. there are not so many black balls in box b as in box C. There are as many red balls in box B as there are in box C.

C. there are not so many red balls in box b as in box C. There are as many black balls in box B as there are in box C.

Answer b

Solution: Only one of the following four situations can occur in each operation:

1. Put the red ball in frame A and the black ball in frame B;

2. Put the black ball in frame A and the red ball in frame C;

3. Put the red ball in frame A and the red ball in frame B;

4. put the black ball in box a and the black ball in box C.

Since there are as many red balls and black balls in the bag, the number of times in case 3 and case 4 must be the same, so it can be concluded that there are as many red balls in box B as there are black balls in box C, so choose B.

Only the case of 1 is the counterexample of options a and d,

Only case 2 is the counterexample of option C.