Alterations in the ratio of cd4: cd8 lymphocytes are associated with risk of hiv infection progressing to aids, of autoimmune diseases, and of progression of some cancers. in searching for predictors of these effects in normal individuals, researchers have found a region of the human genome with 2 markers that are associated with the cd4: cd8 ratio. what does this indicate for the general population? a) one of the markers must be in a gene that affects the cd4: cd8 ratio. b) autoimmune diseases such as type 1 diabetes are caused by a gene in this region. c) this is the only region of the genome that affects the cd4: cd8 ratio. d) the cd4: cd8 ratio is affected entirely by the environment. e) the markers are in linkage disequilibrium with a mutation that affects the cd4: cd8 ratio.

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.