How many structural isomers are possible for a compound with molecular formula $C_3H_7Cl$?

Which of the following is correctly matched?

The number of possible isomers for the molecular formula $C_4H_8$ is .................. .

Identify the correct statements from the following. Choose the correct answer from the options given below.
$A$. Pentan$-3-$one and Pentan$-2-$one are metamers.
$B$. Butanenitrile and Butaneisonitrile are functional isomers.
$C$. Butan$-1-$ol and Butan$-2-$ol are position isomers.
$D$. Butan$-1-$amine and $N$-methylpropan$-1-$amine are homologous.

Which of the following is not an isomer of $but-1-yne$?

The total number of stereoisomers of $1,3-$dichlorocyclohexane is: