We need to find the minimum number of students in a class which can be divided into the group of 5 or 8 or 12 .

The minimum number of students which can be divided into groups of 5 or 8 or 12 can be found by calculating the least common multiple (L.C.M.) of 5, 8 \& 12 i.e. 120.

Hence the minimum number of students in class should be 120 , so the answer is (D).