The valence shell electron pair repulsion (VSEPR) theory is a model used to predict 3-D molecular geometry based on the number of valence shell electron bond pairs among the atoms in a molecule or ion.
We can also remember that VSEPR theory defines the three-dimensional shape of molecules based on the repulsion of electron pairs and the presence of bonds. The VSEPR theory can explain why certain molecules are shaped the way they are in 3D.
Therefore, the answer is VSEPR theory.