You are given the biochemical pathway below. Seven mutant strains (labeled S1 - S7) are defective in this pathway and cannot produce the end product when provided with minimal media. Each mutant strain is defective in only the one step indicated by the path. Select all metabolites that when added to minimal media (one at a time) will allow the mutant strain S7 to produce the end product in the reaction. If none of these metabolites will rescue the mutant strain, select "None of These".