A preschool teacher is rearranging four boxes of playing blocks so that each box contains an equal number of blocks. Currently Box 1 has 32 blocks, Box 2 has 18, Box 3 has 41, and Box 4 has 9. Select the way he could make each box have the same number of blocks. * A . Remove 7 blocks from Box 1 and place them in Box 2. B . Remove all the blocks and make four equal piles of 25, then put each pile in one of the boxes. C . Remove 21 blocks from Box 3 and place them in Box 4. D . Remove 7 blocks from Box 1 and place them in Box 2, and remove 21 blocks from Box 3 and place them in Box 4.