To map genes of a bacterial strain, conjugation must be interrupted at given times. Suppose you have Hfr cells of genotype a+b+c+d+e+strS and F- cells of genotype a-b-c-d-e-strR and you combine these two cultures in liquid medium in four blenders at time 0. After intervals of 3, 6, 9, and 12 minutes, you turn on successive blenders. The resulting cultures were then plated on medium containing streptomycin. Why?A) to eliminate non-conjugated F- cellsB) to eliminate the Hfr cellsC) to selectively eliminate cells that have taken in F+ genesD) to eliminate all non-conjugated cells