In humans, the placenta is essential to the embryo for

Question options:

(1)nutrition, excretion, and reproduction

(2)respiration, nutrition, and excretion

(3)movement, reproduction, and nutrition

(4)coordination, movement, and growth

(2)respiration, nutrition, and excretion

Explanation:

The placenta between the mother and the fetus has three main function.

- Attach the fetus to the uterine wall.

- Provide nutrients to the fetus.

- Allow the fetus to transfer waste products to the mother's blood.

The placenta refers to an organ in the uterus of mother that is responsible for nourishing and maintaining the fetus through the umbilical cord. The placenta also has many other functions but primarily it plays critical roles in the nutrition, respiration and excretion of the fetus. Its other functions include: production of hormones, production of immunity for the fetus for prevention from infections, etc. 

a "theory" a suggestion that is not 100 % accurate, or a figure. some people say its a theory because they of all the passed theory's about one subject. it depends sometimes theory might be accurate and sometimes they are.