In simple harmonic motion force is directly proportional to ...X... of the body from the mean position. Here, A refers to

The simplest type of oscillatory motion is SHM In SHM

$$\begin{gathered} F \propto x \\ {F}_s = –kx \end{gathered}$$

Simple harmonic motion arises when the force on the oscillating body is directly proportional to its displacement from the mean position, which is also the equilibrium position. Further, at any point in its oscillation, this force is directed towards the mean position. Displacement and force are in opposite directions.