All of the following result from overgrazing in semiarid regions except regeneration of grasses soil compaction reduced local rainfall topsoil erosion

regeneration of grasses

Semiarid region are subtype of dryland. These regions are drought regions. The soil in these regions is dry and degraded.  This region receives very low rainfall. The soil lacks essential organic humus, nutrition and appropriate moisture content. Therefore, grasses will not regenerate after overgrazing.

the sphincter muscles at the end of the digestive tract is the anus.

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.