1. The problem statement, all variables and given/known data http://puu.sh/cAjmp/14ba3df23a.jpg [Broken] 2. Relevant equations Acceleration at any instant: -(2*pi*f)^2 * x, where x is displacement from equilibrium and f is frequency. 3. The attempt at a solution Firstly, I know it can't be D as acceleration would increase as potential energy increases, it also can't be B as acceleration is 0 when velocity is at a maximum, or "1", so it isn't in the opposite direction. Where I am confused is at A and C, as they both seem correct to me. When the particle's speed is greatest is when it is passing through equilibrium, and so acceleration will be 0, its least value. But as acceleration is -(2*pi*f)^2 * x, you can say that acceleration is proportional to the frequency. Therefore, they are both right? But the answer is A only.