Final answer:
Charlie's velocity relative to you is 8 m/s.
Step-by-step explanation:
In physics, velocity is a vector quantity that includes both speed and direction. To determine Charlie's velocity relative to you, you need to subtract your velocity from Charlie's velocity. Since you're moving at 10 m/s and Charlie is moving at 18 m/s, his velocity relative to you would be 18 m/s - 10 m/s, which equals 8 m/s. Therefore, the correct answer is B) 8 m/s.