In the Group Work, we measure the restoring force for the pendulum has it is displaced to higher angles of arc. What does it show, and how is it important?

Question $4$ options:

It shows that the restoring force seems to reach a maximum at $90$ degrees of swing, which is as far as a string can swing without going slack.

It shows that the restoring force is only linear for small swing angles. Above this, the pendulum is not a true simple harmonic oscillator.

It shows that the restoring force is non$-$linear, meaning that a pendulum does not act as a simple harmonic oscillator.

It shows that the restoring force is linear, meaning that a pendulum acts as a simple harmonic oscillator.