An Hfr strain is mated with an F- strain. Following conjugation, what are the two resulting strains?
A. F+ and F+
B. Hfr and F+
C. F' and F-
D. Hfr and F-
A. F+ and F+
B. Hfr and F+
C. F' and F-
D. Hfr and F-