The task in science lab: discover which solid substance, without tasting, is sugar. donna and dave have five substances to test, and unfortunately, two are white! "let's heat them! " suggested donna. did donna have a reasonable solution to their problem? a) yes, it would narrow the search to salt or sugar. b) no, all four substances have pretty low melting points. c) no, it's impossible to reach these temperatures in a student lab. d) yes, sugar's melting point is much lower than the other four solids.