The number of molecules, which are nonpolar is ..................... ${\mathrm{SnCl}}_2, {\mathrm{BF}}_3, {\mathrm{BeF}}_2, {\mathrm{OCl}}_2$.

The triatomic molecule,

The presence of lone pair shows it’s polar in nature.

The molecule

The net dipole moment of zero.

The molecule 

The net dipole is zero.

The molecule

Hence, the molecules, $\text{B}{\text{F}}_{\text{3}}$ and $\text{Be}{\text{F}}_2$ are non-polar in nature. So, the correct answer is 2.