Why would it be an advantage for some humans to have malaria or cystic fibrosis

After getting the slide and microscope ready, stella is eager to see the microscopic pond water specimen! she crouches around her microscope and aligns her eye with the microscope’s eyepiece. but she's only able to see a bright white light. at this point, no specimens or cells are visible on stella's pond water slide. after taking a moment to collect her thoughts, stella realizes she can't see any lifeforms because .

The chemical form of energy that is useable by the cell to do work

Plz ! what does it mean for an allele to be dominant?