Lets approach this question through option.
We have to maximize students having 5 score.
Total score = 4.75 * 20 = 95
And, range = 2
Start from maximum possible options.
Option A. If 19 students have 5 score, then sum of score for 19 students will be 19* 5, which is 95. In this case, 1 student who is left has to score 0. But student can score {2,3,4,5} only. Eliminated.
Option B. If 17 students have 5 score, then sum of score for 17 students will be 17 * 5, which is 85. 3 students left and sum of score left is 10.
Now, we have to fulfill the second criteria of question, range =2. So one student must score 3.
17 students scored 5, 1 student scored 3. Students left = 2, score left = 7
We can distribute 7 score among 2 students as 3 and 4.
Final distribution, 5 score -> 17 students, 4 Score -> 1 student, 3 Score -> 2 students
This case is possible (fulfilling all criteria). So B is the answer.