How does the observed amount of normal matter in the universe compare to the amount required to re-collapse the universe?
a. The observed amount of normal matter is about 1/3rd of the amount needed.
b. The observed amount of normal matter equals the amount needed, to within observational uncertainty.
c. The observed amount of normal matter is about twice the amount needed.
d. The observed amount of normal matter is about 1/20th of the amount needed.