Which of the following molecule has zero dipolemoment

(A) BeCl₂ is a linear molecule . It has a bond angle of 180^o. As there are two polar bonds are equal and opposite in orientation, the net dipole will be zero.

(B) $\mathrm{HCl}$ have a dipole moment because the hydrogen atom has a some positive charge and the chlorine atom has some negative charge. There is a small dipole-dipole force of attraction between adjacent $\mathrm{HCl}$ molecules because of the force of attraction between oppositely charged particles.

(C)  ${\mathrm{NH}}_3$ is an asymmetrical molecule, so the dipole moments are not canceled hence there is a net dipole moment in the molecule. Hence, Ammonia is a polar molecule.

(D) ${\mathrm{H}}_2\mathrm{O}$ have bent structure in which the two $\mathrm{O}-\mathrm{H}$ bonds are present at an angle of $104.5^0$, so water is a polar molecule and have a net dipole moment.

Hence, the correct option is (A).