To determine which molecule is non-polar, we need to consider the molecular geometry and the polarity of the bonds.$\\$1. $$POCl$_3: \\$• Phosphorus oxychloride has a tetrahedral geometry.$\\$• The P=O bond is polar, and the P-Cl bonds are also polar.$\\$• Due to the geometry, the dipoles do not cancel out, making POCl$_3$ polar.$\\$2. $$CH$_2$O (formaldehyde):$\\$• Formaldehyde has a trigonal planar geometry.$\\$• The C=O bond is polar, and the C-H bonds are less polar.$\\$• The dipoles do not cancel out, making CH$_2$O polar.$\\$3. $$SbCl$_5: \\$• Antimony pentachloride has a trigonal bipyramidal geometry.$\\$• The symmetry of the molecule allows the dipoles to cancel out.$\\$• Therefore, SbCl$_5$ is non-polar.$\\$4. $$NO$_2: \\$• Nitrogen dioxide has a bent geometry.$\\$• The N-O bonds are polar, and the geometry does not allow for cancellation of dipoles.$\\$• Therefore, NO$_2$ is polar.$\\$Based on the analysis, the correct answer is Option 3: SbCl$_5$ is non-polar.