A certain type of shrimp habitually hovers around superheated deep-sea geysers, near which the bacteria that form the shrimps' diet can be found, Because the geysers emit a faint light, scientists have concluded that the shrimps' light sensitive dorsal patches were developed to locate the geysers and thereby find food. Which of the following, if true, casts the most doubt on the scientists' conclusion? ['The light given off by the geysers too faint to be detected by the human eye', 'In other types of shrimp, a heat-seasing organ has developed that could serve the same geyser-detecting purposes as the light sensitive patches are said to serve.', 'The light to which the shrimps are sensitive is not the sort of light that the geysers emit', "The heat inside a geyser's stream is sufficient to kill instantly any bacteria that move into it"]