In order to test how sea urchin sperm bind to eggs, scientists isolated the egg receptor protein that binds to the sperm acrosomal protein called bindin. Plastic beads were coated with egg receptor for bindin (ERB1) from eggs of the sea urchin Strongylocentrotus purpuratus, and then the beads mixed with sperm from S. purpuratus or from the related species, S. franciscanus. The researchers counted how many sperm were bound to each bead. The results are shown in the graph below. Treatments: A: S. purpuratus sperm mixed with S. purpuratus ERB1 beads B: S. purpuratus sperm mixed with beads containing no ERB1 protein C: S. franciscanus sperm mixed with S. purpuratus ERB1 beads D: S. franciscanus sperm mixed with beads containing no ERB1 protein Based on the description of the experiment, which of the treatments would be considered a "control" treatment for S. purpuratus sperm binding? -triyambak.org