If all of the offspring have roan coats—white hairs mixed into a base coat of red—what can be said about the red and white alleles for coat color?

The alleles for red and white coat color are co-dominant.

Explanation:

Co-dominance is the condition when none of the allele of a gene is dominant. The heterozygous genotype exhibits traits of both alleles.

In the given example, the offspring have roan coat color in which white hairs are mixed into a base coat of red. Since both the alleles are expressed in heterozygous offspring, the alleles for red and white coat colors are co-dominant over each other.

The alleles for red and white coat color are co-dominant.

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.