The total number of structural and stereo isomers for the compound of the formula ${\mathrm{C}}_4{\mathrm{H}}_{10}\mathrm{O}$ is

${\mathrm{C}}_4{\mathrm{H}}_{10}\mathrm{O}$ satisfies the general molecular formula $\left({\mathrm{C}}_{\mathrm{n}}{\mathrm{H}}_{2\mathrm{n}+2}\mathrm{O}\right)$of monohydric alcohols (ROH) and aliphatic ether (ROR').
${\mathrm{CH}}_3{\mathrm{CH}}_2{\mathrm{CH}}_2{\mathrm{CH}}_2\mathrm{OH}$,

 ${\mathrm{CH}}_2-{\mathrm{CHCH}}_3-{\mathrm{CH}}_2\mathrm{OH}$,

 ${\mathrm{CH}}_3-{\mathrm{CH}}_2-{\mathrm{CHCH}}_2\mathrm{OH}$,

 $\mathrm{C}{\left({\mathrm{CH}}_3\right)}_3\mathrm{OH}$ are the monohydric alcohols, and

 ${\mathrm{CH}}_3-\mathrm{O}-{\mathrm{C}}_3{\mathrm{H}}_6$,

${\mathrm{CH}}_3-\mathrm{O}-\mathrm{CH}{\left({\mathrm{CH}}_3\right)}_2$,

 ${\mathrm{C}}_2{\mathrm{H}}_5-\mathrm{O}-{\mathrm{C}}_2{\mathrm{H}}_5$ are the aliphatic ethers adding up to 7 in total.
Therefore, (A) 7 is the correct answer.