Re-order paragraphs

a) The brain is our most treasured possession.

b) It coordinates our movements, our words, our relationships, and the ability to pass on our genes.

c) Our body therefore protects the organ fiercely: The central nervous system polices particles traveling through the bloodstream and invites only the safest into our cognitive chamber.

e) This selective process occurs due to a proactive boundary known as the blood-brain barrier.

d) The barrier serves a vital role, but is also poses a tremendous challenge for scientists developing drugs to treat brain-based disorders.