FC0 is a (+) frameshift mutation in the rII locus. A stock of FC0 is mutagenized with proflavin and plated on a lawn of E. coli K, where only phenotypically wild type phage can grow. You pick one of the plaques and make a stock of it. You would like to determine whether the stocks reversion to rII+ was a true reversion or the result of a second site suppressor mutation. To do this you cross the phage with phage from a wild type stock and plate the progeny on E. coli B. You find that 96% of the plaques are small and 4% large. Based on this data, you conclude that the stocks reversion to rII+ was the result of: A. true reversion.
B. second site suppressing mutation