Which of the following molecules has polar bonds but the overall polarity is zero.

Boron Trichloride or ${\mathrm{BCl}}_3$ is a nonpolar compound because of its symmetrical structure i.e. Trigonal Planar. The B-Cl bond itself is polar because of the difference in electronegativity of Boron(2.04) and Chlorine(3.16) atoms and all three B-Cl bonds lie at 120 degrees to each other.

Hence, the correct option is option (A) ${\mathrm{BCl}}_3$.