Final answer:
The expansion history of the universe is determined by the balance of kinetic and gravitational energies which is influenced by the presence of dark energy, leading to an accelerating cosmological expansion reflected in the cosmological redshift.option b is correct.
Step-by-step explanation:
The expansion history of the universe is predicted by balancing the energy contributions from various sources, including dark energy, dark matter, and ordinary matter. When discussing the dynamics that determine this expansion, scientists focus on the competition between the kinetic energy of the expansion and the gravitational pulling back due to matter. Cosmological redshift is a key observational phenomenon that helps us understand the expansion rate of the universe.
It indicates that distant galaxies are moving away from us, and the more distant they are, the faster they appear to move away. This is consistent with a universe dominated by dark energy, which causes an accelerating expansion over time. As the universe grows larger and matter is spread thinner, the influence of dark energy becomes more significant, leading to increased acceleration in the expansion of the universe. On the other hand, galactic mergers and supermassive black holes play roles in the evolution of individual galaxies but have a lesser impact on the large-scale expansion of the universe.