There are four seasons in China. March, April and May make the spring. June, July and August make the summer season. September, October and November make the autumn season. The rest（剩下）of months make the winter season.

    The Australia seasons are the opposite（相反的）of ours. When it's spring in China, it is autumn in Australia.

    Australia is in the south（南方）of the earth. June, July and August are the winter months. The summer is in December, January and February. It's very hot there, too.

    Near the North Pole（北极）there are two seasons. The winter nights are long. For more than two months you can't see the sun, even at noon. The summer days are long. For more than two months, the sun never sets（落下）, and there's no night.

材料一：塔里木河位于新疆南部，是我国最大的内流河。塔里木河上游段常年有水，不仅水量大，而且水质好，补给量大于排泄量。中游段跑水缺口多，洪水期注入沙丘洼地的积水，几乎全部耗散于蒸发，直接转化为地下水的甚少。下游段因地表水急剧减少，补给更少，所以地下水出现区域性持续下降的趋势。

材料二：下图为塔里木河流域水系示意图。

研究“酸雨对生物的影响”时，所采取的科学方法是（  ）