Answer:
Option B, Electromagnetic radiation
Explanation:
It was during this period , for the first time in 50, 000 years that the density of matter had surpassed the density of electron. It was found that at temperature of 16000 kelvin, the radiation get converted to matter . This era was termed as Matter Era or Atomic Epoch in which the atom form remained intact and hence the the electrons remained attached to nuclei also it was found that Electromagnetic radiation decoupled during this phase.
Hence, option B is correct
