What are CpG islands? DNA regions with many cytosine bases adjacent to guanine bases DNA regions with many cytosine–guanine base pairs DNA regions that are the sites of X inactivation in male mammals DNA regions that remove acetyl groups from histone tails DNA regions that form complexes with acetylase proteins

Where are the options?

Atissue is a group of connected cells that have a similar function within an organism.

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.