To solve this problem, we need to identify the inducer required for the expression of the Lac operon. Let's analyze the options:$\newline \bullet$The Lac operon is a set of genes in bacteria that are involved in the metabolism of lactose.$\newline \bullet$The operon is regulated by the presence or absence of an inducer, which is a molecule that initiates the transcription of the operon.$\newline \bullet$Lactose acts as the inducer for the Lac operon. When lactose is present, it binds to the repressor protein, causing it to detach from the operator region of the operon. This allows RNA polymerase to transcribe the genes necessary for lactose metabolism.$\newline \bullet$Glucose is not an inducer for the Lac operon. In fact, the presence of glucose inhibits the expression of the Lac operon through a mechanism known as catabolite repression.$\newline \bullet$Galactose is not an inducer for the Lac operon. Although it is a component of lactose, it does not directly induce the operon.$\newline \bullet$Therefore, the correct inducer for the Lac operon is lactose.$\newline$Thus, the correct option is Option 3: Lactose.