Concept:A non-polar molecule has no net dipole moment because its charge is evenly distributed.
Explanation:Bromine exists as a diatomic molecule,
Br2.
Both bromine atoms are identical, so they have the same electronegativity.
Therefore, the shared pair of electrons is attracted equally by both atoms.
This produces an equal charge distribution and a net-zero dipole moment.
In contrast, ammonia, water, and hydrogen bromide contain polar bonds and have a net dipole moment.
Answer:A. Bromine