Which of the following best describes what causes water molecules to exhibit properties such as cohesive and adhesive behavior?
a. water molecules are polar, having partially positive and partially negative ends.
b. water molecules have both a hydrophobic end and a hydrophilic end.
c. water molecules are capable of dissolving both polar and nonpolar substances.
d. water molecules have a high molecular weight, making them very dense.

The chemical formula of water is . It is a polar covalent molecule and in each O-H bond, oxygen has a partial negative charge and hydrogen a partial positive charge. Water molecules have strong cohesive forces as they can form intermolecular hydrogen bonds. Water molecules can also show strong adhesive forces with the walls of the container it holds due to the polar nature of the molecules.

So, the correct answer will be A. Water molecules are polar, having partially positive and partially negative ends.