Which of the following compounds is used in antiknock compositions to prevent the deposition of lead oxides on spark plugs,combustion chambers,and exhaust pipes?

Write the structures of different chain isomers of alkanes corresponding to the molecular formula $C_{6}H_{14}$. Also,write their $IUPAC$ names.

The correct order of reactivity of $(I)$,$(II)$,and $(III)$ towards addition reactions is:
$(I)$ Cyclopropane
$(II)$ Cyclobutane
$(III)$ Cyclopentane

Photochemical chlorination of an alkane is initiated by a process of

Which reactive intermediate is involved in the following reaction?
$2-\text{methylbutane} \xrightarrow{Br_2, hv} 2-\text{bromo}-3-\text{methylbutane}$ (not the major product)

Among the isomeric alkanes of molecular formula $C_{5}H_{12}$,identify the one that on photochemical chlorination yields:
$(i)$ $A$ single monochloride.
$(ii)$ Three isomeric monochlorides.
$(iii)$ Four isomeric monochlorides.