Concept:Heat (estrus) is the period when a female farm animal is receptive to mating, shown through specific physical and behavioural signs.Explanation:Common signs of heat include redness and swelling of the vulva, loss of appetite, restlessness, and frequent urination.During heat, the body temperature generally rises slightly, not lowers.Therefore, low blood temperature is not considered a sign of heat in farm animals.Answer:B. low blood temperature