In 1831, charles darwin visited the galapagos islands. while observing the giant land tortoises that lived on these islands, darwin noted that the shape of the tortoise shell varied depending on which island the tortoise lived. tortoises on one island had round shells, for example, whereas tortoises on a neighboring island had more flattened, saddle-shaped shells. which statement best summarizes darwin's explanation for these differences? a) random mutations caused the shape of the shells to fluctuate periodically. b) the shape of the tortoise shell varied because the predators on the islands were all similar. c) the particular shape of the shell was best suited for the island on which the tortoise was living. d) tortoises who used their shells in special ways caused the shells to become larger, rounder, or flatter.

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.