Oxygen is attached to
a) an iron atom located on the heme portion of hemoglobin
b) an iron atom located on the globin portion of hemoglobin
c) a calcium atom located on the globin portion of hemoglobin
d) a calcium atom located on the heme portion of hemoglobin

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.

b is the correct answer

the answer is z.

the human body has five levels of organization. level 1: cells. cells are the basic units of life and form the first level of organization. cells in the human body have specific functions. examples include nerve cells, blood cells, liver cells, and so on.