beneficial, only harmful, only beneficial or harmful
I gave my students this multiple choice question: Some microorganisms cause human disease. Other microorganisms are used in making cheese, yogurt, and bread. Based on this information, the relationship between humans and microorganisms can be

Only one answer is correct among these 4 choices:
- beneficial, only
- harmful, only
- beneficial or harmful

Could you tell me which one is correct?

beneficial or harmful