Explain why a gene pool cannot be made up of only one individual

All the possible alleles for a gene with multiple alleles cannot be expressed by single individual

Explanation:

Gene pool refers to the sum total of all the alleles of all the genes which are present in a population. Human beings are diploid organisms. One individual can have only two possible alleles for a gene. A gene can have two or more than two alleles. Since all the possible alleles for a gene with multiple alleles cannot be expressed by single individual, a gene pool cannot be made of one individual.

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.