In an experimental test of the effects of vitamin B12 on problem-solving performance, is the independent variable and is the dependent variable.

Vitamin C is the independent variable and problem solving performance is the dependent variable.

Explanation:

The independent variable is the variable that can be manipulated or changed to measure its effect. Vitamin C dosage can be changed for difference individuals to see the effect on their problem solving performance.

Dependent variable is the variable on which the effect of independent variable is measure i.e the effect of vitamins C with different dosage will be known or measured base on problem solving performance of an individual.

Therefore ability to solve problems by individual after the intake of vitamin C means its depends on Vitamin C intake.

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.