Use the following information and graph to answer the question.
The figure depicts changes to the amount of DNA present in a recipient cell that is engaged in conjugation with an Hfr cell. Hfr cell DNA begins entering the recipient cell at time A. Assume that a fragment of the recipient cell's chromosome is exchanged for a homologous fragment from the Hfr cell's DNA.
At which time can the recipient cell first be described as "recombinant"?