The functional group can always be found in a carbohydrate molecule

Carbohydrates can contain hydroxyl (alcohol) groups, ethers, aldehydes and/or ketones.

Carbohydrates are chains (or polymers) of basic sugar molecules such as glucose, fructose and galactose. In order to see which functional groups are present in carbohydrates, we must look at the functional groups present in the more basic building blocks. Saccharides - and by extension carbohydrates - are composed of only three atoms: carbon, hydrogen and oxygen. The structure for one of the most common saccharides, glucose, is shown here.

Explanation:

the answer is d. chordata