1. Why is a selectable marker such as antibiotic resistance often used in bacterial genetics experiments involving "crosses" between strains?
A. It allows you to measure the rate of transfer of antibiotic resistance via conjugation.
B. It allows you to select for cells that have integrated the F element.
C. It allows you to distinguish F+ from Hfr strains
D. Having one "resistant" and one "sensitive" strain lets you distinguish the two strains, which otherwise look alike.