第四句：
如今，随着现代城市的发展，传统的四合院已逐渐减少。
译文一
Nowadays, with the development of modern cities, the number of traditional siheyuan has gradually decreased.
思路：“现代城市的发展”是一个从过去一直持续到现在的动作，故时态用现在完成时。“四合院减少”中此处“减少”的是四合院的数量，故需增译the number of使逻辑更加合理。
译文二
Nowadays, traditional siheyuan are gradually disappearing as modern cities continue to expand.
思路：“已逐渐减少”中的“已”暗示变化已经发生且仍在持续，可以用现在进行时 are decreasing 强调动态过程，也可以用现在完成时 have decreased 强调结果。
译文三
Traditional siheyuan are now in decline due to the expansion of modern cities.
