To prove that △DFE ~ △GFH by the SSS similarity theorem using the information provided in the diagram, it would be enough additional information to know that HF is 2 units and GH is 3 units. HF is 3 units and GH is 2 units. HF is 4 units and GH is 2 units. HF is 3 units and GH is 4 units.