Grignard reagent cannot be prepared in an aqueous solution but can be prepared in an ether medium because .............

The correct combination of names for isomeric alcohols with molecular formula $C_4H_{10}O$ is/are:
$A$. tert-butanol and $2$-methylpropan$-2$-ol
$B$. tert-butanol and $1,1$-dimethylethan$-1$-ol
$C$. $n$-butanol and butan$-1$-ol
$D$. isobutyl alcohol and $2$-methylpropan$-1$-ol

In the carbinol system,$sec$-Butyl alcohol is named as:

An example of a compound with the functional group $'-O-'$ is

Identify allylic alcohols in the given examples.

Which of the following are known as mercaptans?