The number of isomers of $C_4H_{10}$ is:

Which of the following compounds possesses both a plane of symmetry $(POS)$ and a centre of symmetry $(COS)$?

Which of the following will have a meso isomer?

Identify the pairs of compounds which are functional group isomers.
$I$. $CH_3-CH_2-CH_2-CH_2-OH$
$II$. $CH_3-CH_2-CH(OH)-CH_3$
$III$. $(CH_3)_3C-OH$
$IV$. $CH_3-CH(CH_3)-CH_2-OH$
$V$. $CH_3-CH_2-O-CH_2-CH_3$
$VI$. $CH_3-O-CH_2-CH_2-CH_3$
$VII$. $CH_3-O-CH(CH_3)_2$

Identify the relationship between the following two structures:

Among the following,identify the compound that is not an isomer of hexane $(C_6H_{14})$: