Dalton's law states that the total pressure exerted by a mixture is the sum of the pressures exerted
independently by each gas in the mixture and that each gasses pressure, or partial pressure, is
directly proportional to its percentage in the mixture. For example:
Gas
Nitrogen
Oxygen
Carbon dioxide
Water
Atmosphere
Alveoli
Percentage; PP (mmHg) Percentage; PP (mmHg)
78.6; 597
74.9;
569
20.9; 159
13.7; 104
0.04; 0.3
5.2; 40
0.46; 3.5
6.2; 47
100% 760 mmHg
100% 760 mmHg
a) What would the partial pressure of each of these gases be at high elevations, where the external pressure is
500 mmHg? If we increased the pressure to 1000mmHg, what are the new partial pressures (PP)? What would
happen to the partial pressure if a person was given 70% oxygen (at sea level)? How would each of these
scenarios affect external respiration (i. e. breathing)?

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.