Final answer:
All these objects emit light and/or heat due to energy transitions, be it from metabolism in humans, electrical excitation in glowing gases of neon signs, or from the heating of metal wires in toasters.
Step-by-step explanation:
The characteristic that a human, hot soup, the metal wires in a toaster, and the glowing gases in a neon sign have in common is that they all emit light and/or heat due to energy transitions. Humans, due to metabolic processes, emit heat similar to the way a light bulb does, though at a less intense rate. The metal wires in a toaster and the glowing gases in a neon sign emit light and heat because of electrical energy heating the metal or exciting the gases, respectively. Neon signs contain gases like neon, argon, or mercury vapor, which emit light of different colors when electrically excited. The emission spectrum of these elements is unique to each and responsible for their specific colors when they are used in gas discharge tubes.