What similarity do nicotine, alcohol, cocaine, and barbiturates share that make them pass the blood brain barrier easily?
a. they are all lipid-soluble molecules.
b. they are all water-soluble molecules.
c. they are all large molecules.
d. they are all small molecules."

D. they are all small molecules

Explanation:Tight cell-wall junctions and a layer of cells around the blood vessels keep large or electrically charged molecules from entering the brain. However, small neutral molecules like those of cocaine and MA easily pass through the blood-brain barrier and enter the brain. Once inside the brain, substances of abuse begin to exert their psychoactive effects.

what are the choices?