Which of the following material offers the lowest resistivity? wood salt water silver lead

Lower resistivity means higher conductivity: among these materials, the best conductor is silver, therefore it must be the material with lowest resistivity among those. We can also have a look at the value of resistivity of the different materials listed in the problem, to check our answer. The resistivities of the materials are the following:
Wood:
Salt water:
Silver:
Lead:
We see that the material with lowest resistivity among those is silver, therefore the correct answer is silver.