for example, the regex [a-zA-Z] only cares about two kinds of characters: letters and everything else. so instead of individually taking derivatives for 52 alphabet characters a..z, A..Z, we can conclude from the start that there are only two kinds of characters we care about: letters ([a-zA-Z]) and non-letters ([^a-zA-Z]).
可没想到，出发的前一天，系统突然发来“行程已被车主取消”的提醒。我一下子慌了神，离返程时间只剩不到一天，临时被爽约再重新找车，难度可想而知。我赶紧重新发布行程，抱着一丝侥幸等待回应。大概过了两个小时，系统终于提示有车主接单，我长舒一口气：“谢天谢地，总算能按时回去了。”可这份安心还没维持半个小时，手机再次弹出消息：车主又取消了订单。看着屏幕上的“行程取消”提示，我心里又气又无奈，如今的顺风车车主，怎么连最基本的契约精神都没有？在这种情况下，我几乎没有主动权，只能被动接受车主的临时变更。，详情可参考PDF资料
«Били в одно место». Российский газовоз уничтожен украинскими дронами в Средиземном море. Что известно об атаке и судьбе моряков14:20，这一点在PDF资料中也有详细论述
Apple 2030 is the company’s ambitious plan to be carbon neutral across its entire footprint by the end of this decade by reducing product emissions from their three biggest sources: materials, electricity, and transportation. iPad Air is made with 30 percent recycled content,8 including 100 percent recycled aluminum in the enclosure and 100 percent recycled cobalt in the battery. It is manufactured with 40 percent renewable electricity, like wind and solar, across the supply chain. iPad Air is designed to be durable and repairable, and also offers industry-leading software support, while meeting Apple’s high standards for energy efficiency and safe chemistry. The paper packaging is 100 percent fiber-based and can be easily recycled.9，详情可参考谷歌浏览器下载