What is the main cause of urban migration in the United States? a. Rural communities are no longer necessary.
b. Urban dwelling provides better access to goods, services, and jobs.
c. Urban communities reduce human impact on the environment.
d. Rural communities are unable to support life in the long-term. .

B

Explanation:

Urban dwelling provides better access to goods, services, and jobs.

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.

it marks things for degradation via the proteasome. it alters there celluar location.