4.
if the offspring of a dihybrid cross have a 9: 3: 3: 1 phenotypic ratio, what must be true of the parents’ genotypes?

both parents are heterozygous for only one trait.

both parents express the dominant trait.

both parents express the recessive trait.

both parents are heterozygous for both traits.

C) reflection (i also looked up the other choices just to make sure)

Mitochondria produce atp, a high energy compound. atp is used for all sorts of enzyme-mediated reactions, such as making proteins/nucleotides/etc, certain compounds cross the cell membrane, muscles move, etc.  without this source of energy, a cell will die. it will not be able to repair itself, defend against pathogens, etc.