2. Models help us develop testable hypotheses because models A. based on things we have never seen
B. very complex and time consuming
C. make out observations more reliable
D. show the relationship between parts of a whole

true is the final answer!

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.

answer///unconditioned stimulus;