Possible structure if a compound like AB4 is polar? I was asked the following question in JEE Mains (2nd September, Shift 1) 2020,

If a compound AB4 is polar (having non-zero dipole moment), then it's structure could be
(A) Square planar
(B) Rectangular planar
(C) Square pyramidal
(D) Tetrahedral

My thoughts

As this compound has only 4 ligands, therefore it cannot be a square pyramidal.
It can neither be a tetrahedral nor a square planar bcoz, it would be non-polar then.

So, we are left only with &quot;rectangular planar&quot;, which I'd never heard before. How to move on?
Given all $\ce{B}$ are equivalent in terms of AXE notation, for $\ce{AB4}$ the following coordination environments are possible [1, p. 177]:

square-planar $(D_\mathrm{4h},$ SP-4);
square-pyramidal $(C_\mathrm{4v},$ SPY-4);
tetrahedral $(T_\mathrm d,$ T-4);
see-saw $(C_\mathrm{2v},$ SS-4).


Table IR-9.3 Polyhedral symbols, geometrical structures and/or polyhedra


Option (A) square planar implies a centrosymmetrical environment and such molecule cannot be polar.
The derivative of (A), option (B) rectangular planar, as well as option (D) tetrahedral also refer to the environments that posses zero dipole moment.
Speaking of (C), I think you are misinterpreting the geometry of square pyramidal coordination.
It's a square non-coplanar arrangement with a non-zero dipole moment commonly seen in period 4 transition metal porphyrins $(\ce{MN4}$ fragment) and also lead(II) oxide and tin(II) oxide $(\ce{MO4}$ fragment).
According to Brecher [2, p. 1944], the structure of bis(N,N-dimethyldithiocarbamato)lead(II) would be yet another example:

Sample depiction of a compound known to exist in square pyramidal configuration:


Since a see-saw option is not present, this leaves only one answer, option (C).
Reference

IUPAC. Nomenclature of Inorganic Chemistry, IUPAC Recommendations 2005 (the “Red Book”), 1st ed.; Connelly, N. G., Damhus, T., Hartshorn, R. M., Hutton, A. T., Eds.; RSC Publishing: Cambridge, UK, 2005.
Brecher, J. Graphical Representation of Stereochemical Configuration (IUPAC Recommendations 2006). Pure and Applied Chemistry 2009, 78 (10), 1897–1970. DOI: 10.1351/pac200678101897.