Ricardo and Monica volunteered to serve food at their church picnic during the 8-10 AM shift. At the end of their shift, they noticed that the kitchen was still pretty busy, so they continued to help through the next shift. Most people would likely say their decision is an example of a(n) action.

Supererogatory action is the answer here.

Supererogatory actions are those acts in ethics that are not morally required. Such acts are good acts. But they are not really necessary.

Supererogatory actions are not duties that are imposed  on people. They are not obligatory.

Ricardo and Monica are not obligated to continue working in the kitchen. But they still made the choice to continue.

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it should be d or b but i'm sure it's d