Shortly after the ball of energy began to expand to form the universe, light elements were formed by which of the following processes? a. chemical changes b. redshift c. cosmic background radiation d. nucleosynthesis

The correct answer is D. Let us analyze briefly each concept in order to justify this answer.

A) Chemical changes are changes in which the nature of the material changes; for example when paper burns. Cutting paper is not a chemical change because the substance of the paper remains the same. When changes are very drastic like the start of the Universe or in radioactive materials, there are nuclear reactions which change the substance and are another category of processes.
B) Cosmic Redshift is an aftermath of the dilation of the Universe. Galaxies that are moving away from us give off a lower frequency light, hence their light is becoming "more red". This is not the cause of the production of light elements.
C) Cosmic Background Radiation is a direct aftermath of the Big Bang and it is predicted by the model. Because we have that at the start, all matter was concentrated together, it was very dense and it radiated. As the Universe dilated, this radiation became less intense, but it is still detectable.
D) Nucleosynthesis is the term we are looking for. It literally means: composition of nuclei. It refers to how protons and neutrons combined in the first 3 minutes to form nuclei of light elements