In carbon dioxide (co2), there are two oxygen atoms for each carbon atom. each oxygen atom forms a double bond with carbon, so the molecule is formed by two double bonds.
two double bonds means that the total number of electrons being shared in the molecule is
two.

Explanation:

Carbon has four electrons in its outer most orbit and it can share four more electrons from other atom to complete its valency while oxygen has 6 electrons in its outermost orbit and it can either charge the electron or gain two electrons from other atom.

Therefore in , the carbon atom shares its two electrons with two electrons of each oxygen atom and forms double bond with it. Thus, total pairs of electron to be shared by the atom of the molecule is two.

regulation of gene expression. gene expression can be regulated by various cellular processes with the aim to control the amount and nature of the expressed genes. these regulatory proteins bind to dna and send signals that indirectly control the rate of gene expression

explanation:

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.