Are sessile animals that have specialized cells called amoebocytes and choanocytes.

Sponges are sessile animals that have specialized cells called amoebocytes and choanocytes.

Sponges (phylum Porifera) are one of the simpllest multicellular organisms (first to branch off the evolutionary tree from the common ancestor of all animals) that have bodies full of pores and channels allowing water to circulate through them. Sponges’ s structure consists of two thin layers of cells and mesohyl layer between them. They don’ t have real tissues or organ systems such as nervous, digestive or circulatory systems. Constant water flow through their openings and pores obtain food and oxygen and remove wastes.

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.