Which of the following is a polyhydric alcohol?

The correct answer is Option (2) → Glycerol

Polyhydric alcohols contain more than one --OH (hydroxyl) group.

A polyhydric alcohol (also known as a polyol) is an organic compound that contains more than one hydroxyl (--OH) group attached to its carbon atoms. Glycerol (propane-1,2,3-triol) is a trihydric alcohol because its chemical structure ($C_{3}H_{8}O_{3}$) contains three hydroxyl groups. In many classification systems, any alcohol with two or more hydroxyl groups---including dihydric and trihydric alcohols---is categorized under the broader term "polyhydric".

Option-wise Detailed Explanation

Option 1: Ethanol ($C_{2}H_{5}OH$)

Structure contains only one --OH group.

Alcohols with one --OH group are called monohydric alcohols.

Hence, not polyhydric.

Option 2: Glycerol ($\text{C}_3\text{H}_5(\text{OH})_3$)

Structure contains three $-\text{OH}$ groups.

Alcohols containing more than one $-\text{OH}$ group are called polyhydric alcohols.

Glycerol is a trihydric alcohol.

Hence, correct.

Option 3: Propanol ($\text{C}_3\text{H}_7\text{OH}$)

Contains only one $-\text{OH}$ group.

So, it is monohydric.

Not polyhydric.

Option 4: Phenol ($C_6H_5OH$)

Contains $-\text{OH}$ group attached to benzene ring.

This is not classified as alcohol, but as phenol because:

$\text{OH}$ is attached to aromatic ring, not alkyl carbon.

Hence, not a polyhydric alcohol.