Some cells contain large numbers of mitochondria while others have relatively few or none. This suggeststhat

A) cells with large numbers of mitochondria are short-lived.
B) cells with large numbers of mitochondria have a high energy demand.
C) cells with small numbers of mitochondria have a large ATP supply.
D) cells with large numbers of mitochondria have a low energy demand.
E) some cells are older than others.