A decrease in conductivity is equivalent to:

When considering the relationship between conductivity and resistivity, it's essential to understand that they are inversely related. Conductivity refers to a material's ability to conduct electric current, while resistivity measures how strongly a material opposes the flow of electric current.

A decrease in conductivity implies that the material's ability to conduct electricity is diminished. This drop in conductivity directly correlates with an increase in resistivity since if a material resists the flow of electricity more, it must hinder the conductance of that current. Thus, as conductivity decreases, resistivity increases, making the answer correct.

In addition, understanding permeability is also important. Permeability relates to how easily a fluid can move through a material, which does not inherently change with electrical conductivity or resistivity. Thus, while the options involving permeability do not accurately reflect the relationship between conductivity and resistivity, recognizing the direct interaction between conductivity and resistivity clarifies why the increase in resistivity is the correct conclusion drawn from a decrease in conductivity.