Which pair of quantities includes one quantity that increases as the other decreases during simple harmonic motion?

acceleration and displacement

acceleration and net force

velocity and displacement

displacement and net force

I believe acceleration and net force not 100% sure sorry if wrong

Velocity and displacement.

Apply the conservation of energy, and you'll see that the maximum kinetic energy equals the maximum spring potential energy

The KE depends on velocity and PE depends on displacement. The KE will decrease as the PE increases and vice versa.

For example, as the maximum displacement is reached, the velocity decreases to 0.

And when the spring returns to 0 displacement, the velocity is at a maximum.