The answer is exemplar model of organizing concepts. It is because the exemplar model was able to make Juan and Sergei correct because this model enables their examples to be appropriate or compatible to the questions being asked. It is a way of saying that the examples that they have been given is the a good example to the question that has been asked, making it correct and reliable.
B. Being new to the country, it is safer for Sarah to take precautions until she gets acclimated
I believe this is the answer as the other answers take too many assumptions as the question doesn't explicitely state that Sarah has skin problems.
15 years for scientist to classify an area's weather as its climate.