Your text describes three types of skeletons explain how a hydrostatic skeleton works

 In organism or animals with hydrostatic skeletons the muscles contract the shape of the coelom and this is the reason there is the movement because of the pressure of the fluid inside the fluid filled cavity. Hydrostatic skeleton this a fluid filled gastrovascular cavity or coelom. It offers resistance and support to the contraction muscles for motility. It is also a structure found mostly in soft bodied animals that consist of a cavity filled with fluid and the coelom, surrounded by muscles.

a

explanation:

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.