Consider the diagram of a mitochondrion shown below.What does the number 4 represent? 
Definitions:
No Child Left Behind
A U.S. Act enacted in 2001 aimed at closing the achievement gap with accountability, flexibility, and choice, so that no child is left behind in their education.
Parental Options
The range of choices available to parents in decisions regarding their children's upbringing, education, and care.
Attention Disorders
A variety of disorders characterized by difficulties in maintaining focus, paying attention, or controlling impulses, often diagnosed in childhood such as ADHD.
Hyperactive
Exhibiting behavior that includes excessive movement, talking, or difficulty with impulse control, often associated with attention-deficit/hyperactivity disorder (ADHD).
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