In humans, chemical digestion is accomplished by enzyme action that begins in the mouth and ends in the
a. esophagus
b. stomach
c. small intestine
d. gallbladder

c. small intestine

Explanation:in humans, digestion is extracellular.specific parts of the digestive system has specific functions.digestion involves the mechanical breakdown and chemical breakdown of food.

These chemicals called enzymes requires specific conditions to be effective.the salivary glands found in the mouth is the first enzyme that food encounters in the digestive system.this gland produces amylase which acts starch.

The stomach mixes food mechanically with enzymes such as the gastric juice containing pepsin.

Digestion initiated in the stomach continues in the intestine,here pancreatic juice from the pancreas and bile from the liver acts on ingested food.

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.