1, assuming there is no such restriction: the "grip strength" item is not measured in the morning and the "step" item is not measured in the afternoon. You can choose from five projects in the morning or afternoon. We can easily get the total number of combinations: 4*5*4*4=320.

2. Consider this restriction: the "grip strength" item will not be measured in the morning and the "step" item will not be measured in the afternoon. Among 320 combinations, it is easy to calculate how many kinds of grip strength there are in the morning, which is110, 32 of the total; Similarly, the number of step combinations in the afternoon is110, which is 32 of the total. So 320-32-32=256 species.

3, but in the end, we have to consider 64 kinds of repeated removal, such as a combination of classmate A, the grip strength in the morning and the number of steps in the afternoon (this is removed twice), and the grip strength of classmate A in the morning and afternoon (also removed twice). B.C.D is needed in this case, so add 2*4-=8.

4, so the final calculation result is 4*5*4*4-32-32+8=264.

You can text me if you don't know. I'll give you a detailed answer. The above two solutions are correct, but it is a little difficult for senior high school students to understand. )