the average temperature of the water samples the brand of microscope slide used the magnifying power of the microscope the proper identification of each microorganism
I gave my students this multiple choice question: Students want to compare the size of microorganism communities in 500-milliliter water samples from each of two ponds. Which factor most likely will affect the accuracy of their observations?

Only one answer is correct among these 4 choices:
- the average temperature of the water samples
- the brand of microscope slide used
- the magnifying power of the microscope
- the proper identification of each microorganism

Could you tell me which one is correct?

the magnifying power of the microscope