Tent caterpillars' routes between their nests and potential food sources are marked with chemical traces called pheromones that the caterpillars leave behind. Moreover, routes from food sources back to the nest are marked more heavily than are merely exploratory routes that have failed to turn up a food source. Thus, tent caterpillars are apparently among the insect species that engage in communal foraging, which consists in the conveying of information concerning the location of food to other members of the colony, nest, or hive. Which one of the following, if true, adds the most support to the argument? ['Sometimes individual tent caterpillars will not return to the nest until a food source is located.', 'The pheromones that tent caterpillars leave behind are detectable by certain other species of caterpillars.', 'A hungry tent caterpillar is more likely to follow heavily marked routes than lightly marked routes.', 'Tent caterpillars can detect the presence but not the concentration of pheromones.']