The correct answer is Option A:

Solution:
Considering the given options.

Option A.    

Option B.     

On Option A:  Considering the given number pattern.

Here, the numbers are increasing.
So, we first find the rule.

Note that:
15 + 5 = 20
20 + 5 = 25
25 + 5 = 30
30 + 5 = 35

So, the rule is "add 5", and this is the required answer.

Hence, the correct counting pattern with the rule ‘add five’ is Option A: