Which one of the following compounds does not give addition reactions?

Hydrocarbon $(A)$ reacts with bromine by substitution to form an alkyl bromide,which by Wurtz reaction is converted to a gaseous hydrocarbon containing less than four carbon atoms. $(A)$ is

$C_2H_6 \xrightarrow{450^{\circ}C} C_2H_4 + H_2$
The above reaction is called:

Describe the preparation of alkanes from unsaturated hydrocarbons.

Halogenation of alkanes is an example of

Excess of isobutane on reaction with $Br_{2}$ in presence of light at $125^{\circ} C$ gives which one of the following,as the major product?