In carrying out normal activities, cells use oxygen and produce carbon dioxide. the concentration of oxygen is higher in the blood than inside the cell, so oxygen moves into the cell. similarly, carbon dioxide moves out of the cell into the blood because the concentration of carbon dioxide inside the cell is greater than the concentration outside the cell. how do the small molecules of oxygen and carbon dioxide move through the cell membrane? a. active transport by carrier proteins b. active transport by endocytosis c. passive transport by osmosis d. passive transport by diffusion

Option D - Passive transport by diffusion

Explanation

The carbon dioxide moves out of the cell into the blood because the concentration of carbon dioxide inside the cell is greater than the concentration outside the cell. The small molecules of oxygen and carbon dioxide move through the cell membrane by passive transport by diffusion. The transfer of particles beyond a membrane without the input of energy is known as passive transport. Diffusion is the diffusion of molecules from an area of high concentration to low concentration across the cell membrane.

the answer is c) an oak tree

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.