▲查了一下教材的原文：

Some festivals are held to honour the dead or to satisfy the ancestors, who might return either to help or to do harm. For the Japanese festival Obon, people should go to clean graves and light incense in memory of their ancestors. They also light lamps and play music because they think that will lead the ancestors back to earth. InMexico, people celebrate the Day of the Dead in early November. On this important feast day, people eat food in the shape of skulls and cakes with “bones” on them. They offer food, flowers and gifts to the dead. The Western holiday Halloween also had its origin in old beliefs about the return of the spirits of dead people. It is now a children’s festival, when they can dress up and go to their neighbours’ homes to ask for sweets. If the neighbours do not give any sweets, the children might play a trick on them.

有些节日是为了纪念死者，或使祖先得到满足，因为祖先们有可能回到世上给人们提供帮助，也有可能带来危害。在日本盂兰盆节，人们要扫墓、烧香，以缅怀祖先。人们还点起灯笼，奏响乐曲，因为他们一位这样做可以把祖先引到世上。在墨西哥，亡灵节是在十一月初。在这个重要的节日里，人们会吃制成颅骨形状的食物，和装点有“骨头”的蛋糕。他们向亡者祭献食物、鲜花和礼品。西方的万圣节也源自人们古老的信念，以为亡者的灵魂会返回人间。万圣节如今成了孩子们的节目，这天他们可以乔装打扮上邻居家要糖吃。如果邻居什么糖也不给，那么孩子们就可以捉弄他们了。

▲根据前后文来看：这里的介词 for 应该是表示陈述或问题的对象，因为前面说了Some festivals are held to honour the dead or to satisfy the ancestors（有些节日是为了纪念死者，或使祖先得到满足），后面针对 the Japanese festival Obon 这一具体节日来作进一步的分析。

当然，若换用介词 on 也不是不可以，则意思稍有不同：它指在盂兰盆节这一天，人们会……