Which of the following is the product of the reaction?

${\mathrm{CH}}_3\mathrm{Cl}+{\mathrm{Cl}}_2\to ?$

${\mathrm{CH}}_2{\mathrm{Cl}}_2$ is formed as a product. A substitution reaction takes place.

Substitution reaction is the process in which one or more hydrogen atoms from a hydrocarbon are replaced by another atom. A saturated hydrocarbon's defining characteristic is substitution reaction (alkanes). 

Example: Chlorine and Chloromethane combine with sunlight to create dichloromethane and HCl.

${\mathrm{CH}}_3\mathrm{Cl}+{\mathrm{Cl}}_2\to {\mathrm{CH}}_2{\mathrm{Cl}}_2+\mathrm{HCl}$