The structure that they are showing is the general structure of an amino acid. If you look at the left side there's NH2 (an amino group). On the right side is COOH (a carboxylic acid group) and the R is the part that varies depending on the amino acid --this way you can make up the 20 different amino acids but all with the basic structure shown in the diagram.
I took the quiz, this is the actual answer. If you look up "general makeup of protein" it will show the same photo. Also, amino acids come together to make up protein.
