Name the functional group present in ${\mathrm{C}}_2{\mathrm{H}}_5\mathrm{COOH}$

In organic chemistry, functional groups are specific group of atoms attached to the molecule that provides their own characteristic property to the molecule.

A simple compound having a carbon-carbon chain is known as an alkane.

Now, ether, aldehyde, ketone, ester, acid, alcohol, and amide are types of functional groups which are shown as:

Thus, a compound classified as ether, aldehyde, ketone, acid, ester, alcohol or amide should have its respective functional group.

Now, the given compound, ${\mathrm{C}}_2{\mathrm{H}}_5\mathrm{COOH}$ has $-\mathrm{COOH}$ group which suggests that it has an acid functional group.

Hence, the correct option is (A).