Concept:A thermopile detects radiant heat energy by converting it into a measurable electrical signal.Explanation:A thermopile is made by connecting several thermocouples in series.When radiant energy, such as infrared or heat waves, falls on its junctions, a temperature difference is created.This temperature difference produces a small voltage.The voltage is then measured to confirm the presence of radiation.Thus, the device is specifically used to detect radiant energy.Answer:B. radiant energy