Asynapse between a motor neuron and a muscle cell uses the neurotransmitter acetylcholine. where is the acetylcholine produced and to where does it travel?

Production of acetyl choline:

The synthesis is done in the nerve fiber itself from choline and acetyl coenzyme A. The choline comes either from the diet or endogenous biosynthesis from serine. Acetyl coenzyme A is a co-enzyme formed in the mitochondria of the nerve cell from the metabolism of carbohydrates.

The synthesis of acetylcholine requires energy but is facilitated by an enzyme: choline-acetyl-transferase. This is synthesized in the cell body and then migrates to the nerve end.

The travel of acetylcholine

After synthesis, acetylcholine is stored in the vesicles of the presynaptic membrane. The number of vesicles in a presynaptic terminus, each containing 1,000 to 50,000 acetylcholine molecules, is estimated at 300,000.

The arrival of an action potential at an axonal termination induces the opening of Ca ++ channels depending on the potential. The ensuing Ca ++ ion entry causes fusion of the vesicles to the plasma membrane and release of the Ach in the synaptic cleft. The ACh then diffuses on the other side of the synapse and by attaching itself on postsynaptic receptors, it causes a modification of the membrane ionic permeability (via ionotropic and / or metabotropic receptors).

a and c are the answeres

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.