Which of the following compounds exhibits tautomerism?

Identify the pairs of compounds that represent chain isomerism among the following:
$I. CH_3-CH_2-CH_2-CH_2-OH$ (Butan$-1-$ol)
$II. CH_3-CH_2-CH(OH)-CH_3$ (Butan$-2-$ol)
$III. (CH_3)_3C-OH$ ($2$-Methylpropan$-2-$ol)
$IV. (CH_3)_2CH-CH_2-OH$ ($2$-Methylpropan$-1-$ol)

The correct statement about the compounds $A$ and $B$ is:

How many structural isomers are possible for the molecular formula ${C_3}{H_7}N$?

Two compounds have the structural formulae $CH_3-O-CH_2CH_3$ and $CH_3-CH_2-CH_2OH$. The above is an example of

The number of metamers possible for $C_{4}H_{10}O$ is