Which of the following functional groups is characterized by a carbon atom double-bonded to an oxygen atom $C_{}=O_{}$ and single-bonded to a hydroxyl group $C_{}-{\mathrm{OH}}_{}$?

Which of the following functional groups contains a nitrogen atom?

Which of the following functional groups is present in alcohols?

Which type of organic compound is the major component of a plant cell wall?

Which of the following functional groups is present in Vitamin A?

Which of the following is not an example of a functional group in organic chemistry?

Which of the following types of molecules are the $A$ and $B$ antigens found on red blood cells?

Which of the following functional groups is present in all amino acids?

Which functional group is commonly found in chemicals that damage the protective ozone layer ($O_3$)?