Please choose the correct answer to the question: Many horses grow a heavy coat in autumn and shed that coat in spring. Scientists were not sure if temperature or the amount of daylight per day (called the photoperiod) caused the change. So, they conducted an experiment and concluded that the change in photoperiod was responsible for the biological changes. Shedding caused by which set of conditions would have helped them arrive at this conclusion?

Answer1: a constant photoperiod, but varied temperatures Answer2: a varied photoperiod, and varied temperatures Answer3: a constant photoperiod, and a constant temperature Answer4: a varied photoperiod, but a constant temperature

Answer format: answer1/answer2/answer3/answer4