Why does passive transport not require the cell to use energy to move molecules across the membrane? The molecules are moving from high concentration to low concentration.

The molecules use water to move across the plasma membrane.

The molecules use protein pumps to move molecules across the membrane.

The molecules are moving against the concentration gradient.

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.

i might be wrong but i think its a. let me know if i’m right and have a good rest of your day!