Question

1 researchers have found that our brains are slower to develop than scientists once thought. one national institute of health project studied over one hundred young people as they grew up during the 1990s. their brain scans revealed that our brains are massively reorganized between the ages of twelve and twenty - five. this is not actual growth, however; in fact, by the age of six, a persons brain is 90 percent of its full size. the adolescent years bring remodeling—much like the upgrade and wiring of a computer network.
2 nerve cells, which link a teens frontal lobe to the rest of the brain, are sluggish. teens lack the amount of the fatty coating called myelin that adults have. this coating can be thought of as a type of insulation, similar to that found on electrical wires. nerves need this substance in order for their signals to flow freely. when myelin is thin and uneven, faulty communication from one part of the brain to another results. this process of neural insulation is thought to be incomplete until a person reaches his/her mid - 20s.
risk - taking behaviors
3 in adults, parts of the brain work in conjunction to evaluate choices and make judgments. teens lack the capacity to make careful choices consistently, since not all parts of their brains are working in unison. while the
how does paragraph 2 contribute to the passage?
by giving necessary details about the brains anatomy
by giving necessary background on scientific brain research
by describing the most significant ages of brain development
by describing the importance of communication within the brain

Explanation:

Paragraph 2 provides details about nerve cells, myelin (a fatty coating), and neural insulation. These are aspects of scientific brain research. It doesn't focus on brain anatomy details (no detailed anatomical structures like lobes' shapes etc. are given), doesn't just describe significant ages (though mentions mid - 20s, it's part of a scientific process description), and while it touches on communication (faulty communication due to myelin), it's more about the scientific background of how the brain (specifically nerve cells and myelin) develops as part of brain research.

Answer:

by giving necessary background on scientific brain research