I want to ask something about human biology. choose the best answer and explain why. u may give the sources.?

1)Which of the following shows the correct arangement of ther blood vessels in accending order of urea concentration in the blood?
A.renal vein,hepatic vein, Vena cava
B.hepatic vein, renal vein,Vena cava
C.Vena cava, renal vein, hepatic vein
D. renal vein,Vena cava, hepatic vein,

2)The movement of the diaphragm is control by
A.cerebrum and cerebellum
B.cerebrum and medulla oblongata
C.spinal cord and medulla oblongata
D.spinal cord and cerebellum

3)Test tube babies:It is found that the embryo had to wait for 2-3 days before transferring into woman's uterus. Why?
A.allow the embryo to develop faster
B. allow the embryo to obtain sufficient nutrients
C. make sure the uterus is ready for implantaion
D. allow the embryo to mitosis, so it will develop into a ball of cells, and thus easier to transfer into uterus