Choose the correct option to complete the given reaction: ${\text{CH}}_2={\text{CH}}_2\text{(g)}+\text{HBr (g)}\stackrel{\text{Ni Catalyst}}{\to }?$

The correct option is B ${\text{CH}}_3{\text{CH}}_2\text{Br}$
The reaction in which atoms combine with unsaturated carbon compounds to form saturated carbon compounds is called addition reaction. Therefore the given reaction is an addition reaction.

The double bond between the carbon atoms will break. Hydrogen atom will get added to one carbon atom and bromine atom will get attached to another carbon atom.

The reaction will occur as follows:

${\text{CH}}_2={\text{CH}}_2\text{(g)}+\text{HBr (g)}\to {\text{CH}}_3{\text{CH}}_2\text{Br (g)}$