The lac operon controls the transcription of a group of genes involved in metabolizing lactose in E. coli. A group of scientists tested how to activate the lac operon. In four different mediums, they varied whether glucose or lactose was present in the medium, as indicated by a or -.The scientist discovered that the lac operon is inducible, repressed by glucose and induced by allolactose. Which medium has the right conditions to metabolize lactose