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 endocytosis
b. active transport by carrier proteins
c. passive transport by osmosis
d. passive transport by diffusion

d. passive transport by diffusion

Explanation:

One of the many functions performed by the plasma membrane is the control of substances entering and leaving the interior of the cell. In this sense, diffusion, also known as molecular diffusion, transports matter in order to maintain the balance between two solutions initially of different concentrations. An example of this can be seen in the question above, which shows the transport of oxygen and carbon dioxide between the inside and outside of the cell. This transport occurs because through diffusion, the cell seeks to balance the concentration of oxygen and carbon dioxide within the cell and in the blood.

Diffusion occurs due to thermal energy present in molecules that constantly move in fluids, whether they are liquid or gaseous. Thermal energy promotes the passage of solute to less concentrated regions. This transport is what allows the cell to absorb various nutrients and also allows any metabolic waste to be excreted.

c. earths continental crust is thicker than its lithosphere.

because, the lithosphere is the outermost layer of the earth/ 100 km thick and is defined by its machanical properties.the lithosphere contains oceanic and continental crust that varies in age and thickness across locations and geologic time. the lithosphere is the coolest layer of the earth in terms of temperature. the term lithosphere should not be confused with the use of "geosphere" which is used to indicate all of earth systems, including the atmosphere, hydrosphere   and biosphere. the surface of the earth can be divided into the continental crust and the oceanic crust.   the continental crust is made mostly of granite while the oceanic crust is made of basalt. the average thickness of the continental crust is 25 miles and the average thickness of the oceanic crust is 5 miles.   three types of rock, igneous, sedimentary, and metamorphic, make up the surface of the earth. that's why 3 option is preferable.