Answer: Option 'A' is correct.
Explanation:
Since we have given that
Total students in a class = 30
Number of students is to be chosen = 4
So, we will use Combination :
As Combination is the collection of the object irrespective of any arrangement.
So, Number of ways to choose 4 students among the 30 students is given by

Hence, Combination is the required answer.
Therefore, Option 'A' is correct.