The CMB Can Be Regarded as a "Wall" Beyond Which

Multiple Choice

The CMB can be regarded as a "wall" beyond which we cannot see light because

A) photons couldn't leave the hot plasma before the recombination period.
B) we haven't discovered the technology to detect light from earlier epochs.
C) galaxies absorb all the photons from earliest times, closer to the Big Bang.
D) there existed only massive particles within the universe in the first 380,000 years of existence; there were no photons.
E) behind the CMB "wall" there is a huge black hole that doesn't allow light to escape.