Final answer:
A lone electron pair affects the molecular shape by pushing bonding electron pairs away, altering the molecular geometry and reducing bond angles.
Step-by-step explanation:
The lone electron pair on the central atom in a molecule affects the molecular shape by causing a repulsion that pushes bonding electron pairs away. This results in a distortion of the idealized molecular geometry to accommodate the space lone pairs occupy. The presence of a lone pair reduces the bond angle between adjacent bonding pairs, altering the electron-pair geometry and molecular structure. For instance, in the molecular geometry designated as AX₂E, where E represents a lone pair, the structure shows that a lone pair occupies more space around the central atom than a bonding pair. This is due to the fact that a lone pair is not shared between two nuclei, creating greater repulsion when compared to bonding pairs. Therefore, the correct answer to the student's question is:
B. The lone pair pushes bonding electron pairs away.