Greg has several siblings that all look very different from one another. However, he can see different traits from his mother and father in each of them.
What contributed to these differences between his siblings?

A. Both prophase 1 and prophase 2 occurred during the formation of his parents' sex cells.
B. Independent assortment occurred during the formation of his parents' sex cells.
C. Independent assortment occurred during fertilization of each egg cell.
D. In mitosis during growth, crossing over caused each child to develop differently.

B

Explanation:

Independent assortment and segregation of chromosomes during meiosis resulted in recombinant chromatids forming that resulted in gametes formed being vastly different from the original sequence of the chromosomes (gene locus remains constant but gene sequence changed) resulting in resultant zygote to have different alleles which resulted in both siblings being different.

However, both siblings looks like their parents as zygote formed are a combination of 1 unit of chromosomes from each parent. Hence, offsprings will have traits from each parent.

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.