The answer is B: 41.

The rule
Add 5, then add 8, then 5, then 8, and so on. The pattern of adding takes turns.
The pattern as Python code
Here is a tiny Python program that follows the same rule. Type it into IDLE and run it to print the whole pattern, including the answer.
adds = [5, 8]
number = 2
for step in range(7):
print(number)
number = number + adds[step % 2]
When you run it, Python prints:
2 7 15 20 28 33 41
Pixel says: Try changing a number in the code and run it again. Can you make the pattern go on for 20 steps? Meow!