old cultures variation

例句：

1. 1. The population of thecity has been increasing over the past decade.
   过去十年里，这个城市的人口一直在增加。
2. 2. The scientists have made significant progress intheir research.
   科学家们在他们的研究中取得了重大进展。
3. 3. The color of the flowers varies greatlydepending on the season.
   花朵的颜色根据季节有很大的不同。