使用条件从句表达因果关系，语义清晰，易于理解。
Once upon a time, a young man kindly took in a wild horse and a donkey. To show their gratitude, the horse and the donkey often helped the young man pull carts and grind flour.
As years passed, the once-young man grew old and became a frail elderly man with limited mobility. The horse and the donkey thought to themselves, "We have already done so much for him. Now that he is old, why should we continue to serve him?" Consequently, they began to play tricks on him.
One day, the old man was riding the horse and leading the donkey through the streets. He had no idea that the horse and donkey had conspired to bully him. As they were walking, the horse suddenly leaped into the air and bucked violently, throwing the old man hard to the ground. Seizing the moment, the donkey kicked fiercely at the old man's head. While dodging the attacks, the old man struggled to crawl up, cursing them for their ingratitude. Just then, a passing wasp saw how the horse and donkey were treating the old man and felt that such ingratitude was intolerable. It flew in front of them and said, "How can you treat your benefactor this way? If it weren't for this man's kindness in taking you in, you would have starved to death in the wilderness long ago!" The horse and donkey dismissed the wasp, saying, "Mind your own business, you little thing!" Furious, the wasp stung them sharply. In a rage, the horse and donkey lunged at the wasp at the same time. The wasp, quick as a flash, flew toward a small river on the opposite side. Driven by fury, the horse and donkey failed to notice the river ahead and fell into the water, eventually drowning after struggling for a few moments.
The wasp sighed and said, "Those who are ungrateful will never meet a good end."
从前，有个小伙子好心收留了一匹野马和一匹驴。为了报答这份恩情，马和驴经常帮小伙子拉车、磨面。
时光荏苒，当年的小伙子已变成了一个行动不便的老汉。马和驴心想：“我们已经为他做了这么多年，既然他已经老了，我们为什么还要继续为他劳作呢？”于是，它们开始故意刁难这位老汉。
一天，老汉骑着马，牵着驴子走在街上。老汉完全没料到，马和驴早已串通好了要欺负他。正走着，马突然腾空跃起，剧烈摇晃，将老汉狠狠摔在地上；驴也趁机向老汉的头部猛踢。老汉一边狼狈躲闪，一边吃力地爬起，嘴里咒骂着它们的忘恩负义。这时，一只路过的马蜂见马和驴竟如此对待恩人，深感愤慨，认为这种恩将仇报的行为实在太过分。它飞到马和驴面前说：“你们怎能这样对待恩人？若非当年老汉好心收留，你们恐怕早就饿死在荒郊野外了！”马和驴却不屑一顾，叫嚣道：“你这个小东西，管不着我们！”马蜂大怒，上前狠狠地蛰了它们几下。马和驴被蛰得急眼了，几乎同时扑向马蜂。马蜂见状，迅速飞向对面的小河。马和驴追得太急，完全没注意到前方的河流，结果双双落水，扑腾了几下便淹死了。
马蜂叹了口气说：“忘恩负义的人，终究不会有好下场。”