Final answer:
The Big Bang is the scientific consensus for the origin of the universe, which occurred about 13.7 billion years ago. It represents an expansion of space, supported by cosmic background radiation and other observations. Therefore the answer is d) It marked the origin of the universe.
Step-by-step explanation:
The prevailing consensus among astronomers and physicists regarding the occurrence of the Big Bang is that it marked the origin of the universe. According to current cosmological models and substantial evidence, the universe began with the Big Bang approximately 13.7 billion years ago. This event was not an explosion in space but a rapid expansion of space itself.
After this expansion, the universe was hot and dense, and it has been cooling and expanding ever since. Cosmic background radiation, which provides compelling evidence for the Big Bang, has a perfect blackbody spectrum characteristic of a temperature of 2.725 K. A significant milestone that offers strong support for the Big Bang theory happened about 380,000 years after the initial event, when the universe became transparent to radiation, allowing us to observe the cosmic microwave background today.