When the blood sugar levels return to normal, the pancreas stops releasing insulin. Is this a negative or positive feedback mechanism?

Negative feedback mechanism

Explanation:

Negative feedback mechanism occurs when the product or the output of a process inhibits the same process. When blood glucose level rises, body receptors stimulate beta cells in pancreas to release insulin. Insulin leads to uptake of glucose by cells, lowering the blood sugar levels. The lowered blood sugar level is again sensed by the receptors and they inhibit the secretion of insulin. Hence, insulin inhibits its own secretion by removing glucose from blood which makes it a negative feedback mechanism.

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.

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