The most common of the psychoactive substances, used by 90% of americans, is

The answer is caffeine. Caffeine is used as a stimulant to maintain alertness and reduce drowsiness. Caffeine is used to improve performance and most take it to allow them to continue working when they naturally feel tired or to stimulate the brain in the morning.  It is consumed in beverages such as tea, coffee, and soft drinks.

answer:

the water molecules are transferred from the roots to the stem or top parts of the tall tree because of important properties of water which are adhesion, cohesion and capillary action. cohesion is the property of water molecules keeps water molecules in a combined state by sharing of bonds between them at the atomic level. adhesion allows the interaction of water molecules with other substances or substrate. adhesion will cause the attachment of water molecules to the wall of the vessel (xylem) of the plant. capillary action occurs when the adhesive force to the vessel wall is stronger than the cohesive force between water molecules. capillary action mimics the transfer of water from a tube or pipe. in this way water utilizes its property to transfer water from down to top level of the plant.