朋友来到这个城市时,因为一时找不到工作,经人介绍,担负起了一个小区的楼道清洁工作。所谓的楼道清洁,主要是将楼道内各家各户放在门外的垃圾清运到小区的垃圾箱内。清运垃圾的工作虽然又累又脏,但总可以从一袋袋垃圾中翻找出一些可以卖的废品,增加一份额外的收入,他很珍惜这份工作。大约一周后的一天,一家住户门外放了三袋垃圾,他像以往一样将几袋垃圾集中装进一个大袋子中,以方便提拿。这时,他却发现三个垃圾袋中的垃圾各不相同,一个垃圾袋中是纯粹的生活垃圾,一个垃圾袋中是 When a friend came to this city, because he could not find a job for a moment, after being introduced, he took up the cleaning of corridor in a community. The so-called corridor cleaning, the main corridor is the various households on the door outside the garbage removal to the community’s garbage cans. Although the work of removing and transporting trash is tiring and dirty, it is always possible to find out some waste products that can be sold from a bag of trash and add an extra income. He cherishes this job very much. About a week later, three bags of rubbish were placed on the door of a household, and he packed a few bags of rubbish into a large bag, as usual, for easy handling. At this moment, he found out that the rubbish in each of the three rubbish bags was different. In a rubbish bag, pure rubbish wastes and in a rubbish bag