Why Is It That Coca Chewing Produces Few Instances of Toxicity

Why is it that coca chewing produces few instances of toxicity?

A) Little cocaine is distributed to the brain,since absorption from the digestive system is slow.
B) There is a chemical found in coca leaves which dilutes the small amount of cocaine found in the leaves.
C) As coca leaves are chewed,the cocaine is absorbed through the cheek linings,bypassing absorption in the digestive tract.
D) Ingestion of coca products never results in toxic effects.