If a met thr Hfr strain is mated with an F of genotype leu thi, prototrophic recombinants can be detected by plating the mixture on:___________
A) minimal medium.
B) minimal medium supplemented with leucine and methionine.
C) minimal medium supplemented with leucine and thiamine.
D) minimal medium supplemented with methionine, threonine, leucine, and thiamine.
E) minimal medium supplemented with threonine and thiamine.