Mass movement that involves rock and soil moving as a single unit a. creep c. landslide b. mudflow d. slump

The right option is; d. slump  

Mass movement that involves rock and soil moving as a single unit is a slump.

A slump is a type of mass movement in which rock and soil materials are moved as a large consolidated block down a slope. Slumps usually occur when a slope is undercut without any support at its base or when there is addition of excessive weight (loading) to a slope that is not stable. Other causes of slumps include freezing and thawing, thorough wetting (such as by heavy rainfall) and earthquake shocks.  

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.