To control chloe's nausea chloe's doctor gives her zofran which blocks the action of serotonin a chemical involved in the bodys nausea response

The medical which is prescribed by chloe's doctor as a/n Agonist.

Agonist is termed as the chemical which is bonded to a receptor whereby its work is to activate the receptor by producing biological response.

There are different types of agonists for example, receptor which is activated by exogenous or endogenous agonist which are neurotransmitter and hormones.

Other types of agonist are full agonists, selective agonist, superagonist and partial agonist.

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.