Most of the energy in the Universe today is...

Question

- contained in the motion of galaxies.
- released through supernova explosions.
- in the form of dark energy.
- the energy of the CMB photons.

Answer 1

http://www.universetoday.com/98864/do-we-really-need-dark-matter/

http://en.wikipedia.org/wiki/Dark_energy

Your teacher probably wnats you to say "dark energy". However, this is a hypothetical energy-matter. There are a number of smart folks who are doubting this hypothesis, and as it stands now, there is little observational evidence that confirms this hypothesis.