Which of the following sentences has a gerund?
① Flying planes is not something that he can handle.
② Flying birds are sometimes very dangerous for flights in the air.
③ He depends too much on his wife and even boiling water is out of his mind.
④ Boiling water would make the kettle whistling.
题干的意思是：下列哪些句子含有动名词。动名词作定语时，表示它所修饰的名词的性能和用途， 和它所修饰的名词在逻辑上没有主谓关系；现在分词作定语时，表示它所修饰的名词正在进行的动作，和 它所修饰的名词在逻辑上有主谓关系。句子② 和 ④ 中的flying和boiling都是现在分词。因此，本题的正确 答案为A。