Given this data, jackson concludes that only unknown 2 could be a protein. which of the following explanations supports jackson's conclusion?

Jackson performed an experiment in which he analyzed the elemental components of several unknown compounds. His results are shown in the table:
Jackson concludes that only Unknown 2 could be a protein. 
Of the explanations that supports Jackson's conclusion is :

B. Proteins have some amino acids that contain sulfur, whereas most lipids, nucleic acids, and carbohydrates do not contain sulfur.