How does the structure of the alveoli allow for it's function if gas exchange

Alveoli can be described as small air filled sacs that are present at the end of the respiratory tree in the lungs.

They have single layer of epithelial cell, which allows rapid gaseous exchange.

Moreover, alveoli are lined by surfactant that is mixture of proteins and lipids that reduces the surface tension within alveoli, increasing the overall surface area for the exchange of gases.

Thus, structure of alveoli ( numerous tiny, round air filled sacs, increasing overall surface area for the exchange) allows for its function.

Alveoli play important role in the respiratory system as they are involved in the gaseous exchange (oxygen and carbon dioxide) to and from the blood that is coming to the lungs.

By doing so, they help in the purification of blood (by taking carbon dioxide from deoxygenated blood and giving it oxygen to make it oxygenated/ pure).

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.