The simplified model of the hall effect proved that the current (electric) in metals are carried by electrons and not protons. The hall effect introduced the hall coefficient which is the ratio of the induced electric field to the current density x applied magnetic field. This coefficient is unique for each type of metal.
Catalyst increases the rate of a chemical reaction
I would say CuSO4 or Copper Sulfate, as option 1 is Methane and would create a fire so heat, and the last one is Sugar which doesn't conduct electricity. And C6H6 I believe is not soluble in water.<span />
