What force causes individual molecules of the same type to attract and stick together?

The correct answer is cohesion, which refers to the intermolecular forces that cause molecules of the same substance to attract and stick together. This force is primarily due to hydrogen bonding in water molecules, leading to phenomena such as surface tension. For example, water droplets form on a surface because the water molecules are attracted to each other and tend to stay together rather than disperse.

Understanding cohesion is vital in many biological processes, such as the movement of water through plant capillaries or the formation of cellular structures where molecules need to stay close together for proper function. Through cohesion, organisms can maintain the integrity of fluids and cellular environments necessary for life.

The other options focus on different interactions and mechanisms. Adhesion refers to the attraction between different substances, coalescence typically describes how two droplets merge to form a larger droplet, and aggregation involves a collection of particles coming together, which can include different types of molecules. None of these concepts directly refer to the attraction of similar molecules to one another, which is why cohesion is the clear choice.