The mass extinction that was most likely caused by the formation and retreat of glaciers was the extinction
a. cretaceous- tertiary
b. end triassic
c. permian- triassic
d. late devonian
e. ordovician- silurian

The correct answer is b

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.