Which of the following has the highest knocking property?

$Methane$ can be converted into $ethane$ by the reactions

Pick out the alkane which differs from the other members of the group.

The number of secondary hydrogens in $2, 2-$dimethylbutane is

The decreasing order of boiling points of the following alkanes is:
$(a)$ Heptane
$(b)$ Butane
$(c)$ $2-$methylbutane
$(d)$ $2-$methylpropane
$(e)$ Hexane
Choose the correct answer from the options given below:

Which of the following gases has the highest heat of combustion?