The big bang theory suggests that our universe formed approximately years ago.

The big bang theory suggests that our universe formed approximately 13.77 billion years ago.

Explanation:

The big bang theory is the theory that explains the origin of our universe and its formation. This theory says that the universe was born approximately 13.77 billion years ago, from a very small, dense, hot point of matter and energy (called singularity) that expanded in all directions in a very short time. All the matter and energy of the universe were originally concentrated in this singularity, and later expanded in order to form the structures that we know nowdays: subatomic particles first, then atoms, molecules, compounds, and later on some more complex structures, such that planets, stars and galaxies.

d is the correct answer