What is the name of the aldehyde corresponding to methane?

The general formula of three compounds $A, B$ and $C$ is $C_{n}H_{2n}$. $B$ has the highest boiling point and $C$ has the lowest boiling point.
$(i)$ Mention the type of compound $A, B$ and $C$.
$(ii)$ Which of these has the minimum number of carbon atoms?
$(iii)$ Name the homologous series to which $A, B$ and $C$ belong.

What is used to preserve the dead bodies of animals?

Which of the following is not a straight chain hydrocarbon?

The molecular formula of $A$ is $C_{10}H_{18}$ and $B$ is $C_{18}H_{36}$. Name the homologous series to which they belong.

Which of the following is the correct match between List-$I$ and List-$II$?

List-$I$	List-$II$
$1$. Hydroxyl group	$a$. $>C=O$
$2$. Aldehyde group	$b$. $-OH$
$3$. Carboxylic acid group	$c$. $-CHO$
$4$. Ketone group	$d$. $-COOH$