The correct option is B X={y:y=5a,a∈N,a≤5}
Given X={5,10,15,20,25}
Identifying the pattern, we see the elements to be first 5 multiples of 5.
In Set-builder form, if we assume y to be the elements of the set, we can write the set as:
X={y:y=5a,a∈N,a≤5}