If AB4 molecule is a polar molecule, a possible geometry of AB4 is:

🧠 For an $\ce{AB4}$ molecule to be polar, the arrangement of 4 identical B atoms around A must be asymmetric so that bond dipoles do not cancel.

• Tetrahedral AB4 (symmetric, all B equivalent) → bond dipoles cancel → nonpolar ✗
• Square planar AB4 (symmetric, all B equivalent) → bond dipoles cancel → nonpolar ✗
• Square pyramidal AB4 (A sits at the apex above the square base of 4 B atoms, with a lone pair occupying the position below A): the A atom is displaced from the geometric centre → the 4 bond dipoles point outward symmetrically in the base but there is an asymmetry along the axis → net dipole → polar ✓

⚡ A real example: if a central atom A has 4 identical B bonds and 1 lone pair arranged square pyramidally, the lone pair creates the asymmetry that gives a net dipole.

$\boxed{\text{Answer: (a) Square pyramidal}}$