Concept: The question tests on the area of Counting

Solution:

Supposing all 3 will join. Then we have to choose 2 more students from the remaining 7 in 7C2 ways = 7 * 6 / 2 = 21

Supposing all 3 don't joint, then we have to choose 5 from the remaining 7 students in 7C5 = 7C2 = 21

Total number of ways = 21 + 21 = 42

Option D