Reproductive isolation:
a) Means there is no gene flow between two groups of organisms.
b) Is necessary for species to remain separate.
c) Is maintained by certain prezygotic and postzygotic barriers.
d) All of the choices are correct.
e) None of the choices are correct.

The answer is b

Explanation:

This is because the species need to remain separated from each-other for this to work

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.

several tissues working together form an organ, and several organs together make up an organisms.

the group of cell that carries out special jobs are tissue.