The correct answer is D) red flares. Signaling devices required on inflatable liferafts include red flares, which are pyrotechnic devices that produce a bright red light and are used to signal distress. This requirement is specified in the regulations governing safety equipment for inflatable liferafts, as red flares are an effective way to attract the attention of rescue aircraft or vessels. The other answer choices are incorrect because a rocket shoulder rifle is not a standard signaling device for liferafts, an oil lantern would not be an effective signaling device, and an air horn, while potentially useful, is not a required signaling device for inflatable liferafts.