Answer:
4
Step-by-step explanation:
The period is the length of one cycle.
By cycle, I mean the smallest piece that can be traced and copied over and over to form the whole graph. If you notice the graph starts at x=0 and the curve makes a complete cycle by x=4. The cycle starts over again at x=4 and ends at x=8. I hope you are seeing the graph looks exactly the same from x=0 to x=4 as x=4 to x=8.
The length of one cycle of this graph is 4.
Please let me know if you have further questions about this question.
Thank you.