Why is evolution necessary

Knowing the evolutionary relationships among species allows scientists to choose appropriate organisms for the study of diseases, such as HIV. Scientists are even using the principles of natural selection to identify new drugs for detecting and treating diseases such as cancer.

Explanation:

the peripheral nervous system or pns contains the nerves, which leave the brain and the spinal cord and travel to certain areas of the body. the peripheral nervous system's main job is to send information gathered by the body's sensory receptors to the cns as quickly as possible.

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.