What is catenation?

$A$ sample of $2,3-$dibromo$-3-$methylpentane is heated with zinc dust. The resulting product is isolated and then heated with $HI$ in the presence of red phosphorus. Indicate the structure that represents the final organic product formed in the reaction.

$2-$Methylbutane on reacting with bromine in the presence of sunlight gives mainly:

Identify the initiation step$(s)$ $(X)$ and termination step$(s)$ $(Y)$ of free radical chlorination of $CH_4$ from the following:
$a) \dot{C}H_3 + \dot{Cl} \rightarrow CH_3-Cl$
$b) \dot{Cl} + \dot{Cl} \rightarrow Cl_2$
$c) \dot{C}H_3 + Cl_2 \rightarrow CH_3-Cl + \dot{Cl}$
$d) Cl_2 \rightarrow 2\dot{Cl}$
$e) CH_4 + \dot{Cl} \rightarrow \dot{C}H_3 + HCl$
$f) \dot{C}H_3 + \dot{C}H_3 \rightarrow CH_3-CH_3$

The boiling points of three saturated hydrocarbons $A, B$ and $C$ are $-102\,^{\circ}C, -43.44\,^{\circ}C$ and $-0.6\,^{\circ}C$ respectively. The hydrocarbon containing the highest number of carbon atoms is .......

Which type of hydrogen atoms are present in $(CH_3)_3CH$?