are agents in the that can reach the fetus through the mother and cause harm. A.
Spermicides . . . bloodstream
B.
Abruptio placentae . . . placenta
C.
Teratogens . . . environment
D.
Proteins . . . bloodstream

c

Explanation:

I hope this help and i am sorry if you get it wrong

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.

they had the law tat factories that produces smoke cannot be built near residential buildings.

building of proper sewage system was done to ensure that the waste is carried away from the humans so that they do not get diseases from it.

also they built water systems to provide water in those areas which are drought prone.