clean the lenses with your fingers keep switching the magnifications carry the microscope with two hands at all times make sure to put the microscope on an uneven surface
I gave my students this multiple choice question: Which safety measure should a student take when handling a microscope?

Only one answer is correct among these 4 choices:
- clean the lenses with your fingers
- keep switching the magnifications
- carry the microscope with two hands at all times
- make sure to put the microscope on an uneven surface

Could you tell me which one is correct?

carry the microscope with two hands at all times