The more ___, the greater the conductivity.

The relationship between conductivity and the presence of ions is fundamental to understanding how electrical conductivity works in liquids. Conductivity refers to the ability of a solution to conduct electric current, which is largely determined by the concentration and mobility of charged particles, known as ions.

When there are more ions present in a solution, the pathways for electric current flow are significantly enhanced. Ions are charged particles that can move freely in the solution, allowing electricity to flow more easily. This is why solutions with higher concentrations of electrolytes, such as salts, exhibit greater conductivity.

In contrast, while water itself is a good solvent, pure water has very low conductivity because it contains very few ions. Temperature generally affects the movement of ions – it can increase their energy and mobility, thereby enhancing conductivity; however, it does not change the fundamental aspect that conductivity is primarily driven by the number of available ions. Likewise, pressure does not have a direct correlation with conductivity in the same way that ion concentration does.

Thus, greater ion presence directly correlates to increased conductivity, making it the most accurate choice among the options provided.