Which one of the following accurately describes the lac operon? a. rna polymerase is prevented from transcribing the lac genes when lactose is present. b. rna polymerase transcribes the lac genes when lactose isn't present. c. the repressor protein binds to the operator when lactose is present. d. the repressor is freed from the operator when lactose is present.

The lac operon, which stands for Lactose operon is known as an inducible system. It is the an operon required for the transport and metabolism of lactose some enteric bacteria (Echerichia coli for example). The Lac operon is only activated in the presence of a key molecule. The key molecule is lactose.
From the given options the following best describes the Lac operon:

D. The repressor is freed from the operator when lactose is present.

the level of progesterone is low at the pre-ovulatory phase of the cycle but it gradually increases and the levels are high at the luteal phase. if pregnancy occurs, the level of progesterone will be high throughout the pregnancy.

if egg is fertilized and the mother gets pregnant, progesterone starts preparing the uterus for the implantation. it starts building up the lining of uterus and make it hostile of the period of pregnancy.