Let's analyze each option to determine the correct answer.$\\$Option 1: Dipole moment of NF$_3$ is greater than that of NH$_3. \\$• NF$_3$ and NH$_3$ both have pyramidal shapes, but the dipole moments are affected by the direction of the dipoles.$\\$• In NH$_3,$ the dipole moment is towards the nitrogen due to the lone pair, resulting in a net dipole moment.$\\$• In NF$_3,$ the dipole moments of the N-F bonds are directed towards the fluorine atoms, which partially cancels the lone pair's dipole moment.$\\$• Therefore, the dipole moment of NH$_3$ is greater than that of NF$_3. \\$This option is incorrect.$\\$Option 2: Three canonical forms can be drawn for CO$_3^{2-}$ ion.$\\$• The carbonate ion (CO$_3^{2-})$ has three resonance structures.$\\$• Each structure has one double bond and two single bonds, with the double bond rotating among the three oxygen atoms.$\\$• This delocalization of electrons stabilizes the ion.$\\$This option is correct.$\\$Option 3: Three resonance structures can be drawn for ozone.$\\$• Ozone (O$_3)$ has two major resonance structures, not three.$\\$• Each structure involves a double bond between one pair of oxygen atoms and a single bond with the other, with the position of the double bond alternating.$\\$This option is incorrect.$\\$Option 4: BF$_3$ has a non-zero dipole moment.$\\$• BF$_3$ is a trigonal planar molecule with symmetric charge distribution.$\\$• The dipole moments of the B-F bonds cancel each other out, resulting in a net dipole moment of zero.$\\$This option is incorrect.$\\$Therefore, the correct answer is Option 2: Three canonical forms can be drawn for CO$_3^{2-}$ ion.