<p>Could you help me explain why the answer is B? f(x+5) = f(x) doesn't make sense.
I think it's A.</p>
<p>Thanks alot!!!</p>
<p>it's B. The function repeats itself every 5 numbers on the x-axis. Since it crosses the x-axis 4 times (where x=0) in one set of 5, then it crosses 8 times in two sets of 5. Now you have 10 but need to go to 12. You can see it only crosses the x-axis once before 2 (this is to reach 12), so add that to the current 8 you already have to get nine.</p>