Lithium is the lightest or is considered as the least dense metal with a density of 0.534 g/cm³ which is comparable to the density of a pine wood. More the amount of density, more amount of mass that particular element has. Density is the ratio of mass to volume, or it tells how much matter is packed in a given area. Palladium is a heavy metal with 12.02 g/cm³. Therefore, it has more density or more mass than lithium so it would definitely be difficult to carry around palladium than lithium. palladium has high mass to volume ratio than lithium.
Thus, with respect to palladium, Lithium being a light metal can be carried around easily.
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 />
