单项选择题 Can a small group of drones（无人机）guarantee the safety and reliability of railways and,at the same time, help railway operators save billions of euros each year? That is the very likely future of applying today's "eyes in the sky" technology to making sure that the millions ofkilometres of rail tracks and infrastructure（基础设施）worldwide are safe for trains on a 24/7 basis.Drones are already being used to examine high-tension electrical lines. They could do precisely the same thing to inspect railway lines and other vital aspects of rail infrastructure such as the correct position of railway tracks and switching points. The more regularly they can beinspected, the more railway safety, reliability and on-time performance will be improved. Costs would be cut and operations would be more efficient（高效）across the board.That includes huge savings in maintenance costs and better protection of railway personnel safety. It is calculated that European railways alone spend approximately 20 billion euros a year on maintenance, including sending maintenance staff, often at night, to inspect and repair the railinfrastructure. That can be dangerous work that could be avoided with drones assisting the crews'efforts.By using the latest technologies, drones could also start providing higher-value services for railways, detecting faults in the rail or switches, before they can cause any safety problems. To perform these tasks, drones for rail don't need to be flying overhead. Engineers are now workingon a new concept: the rail drones of the future. They will be moving on the track ahead of the train,and programmed to run autonomously. Very small drones with advanced sensors and AI and travelling ahead of the train could guide it like a co-pilot. With their ability to see ahead, they could signal any problem, so that fast-moving trains would be able to react in time.What does "maintenance" underlined in paragraph 3 refer to?

单项选择题 总结是单位或个人对过去一个时期内的实践活动作出系统的回顾归纳、分析评价，从中得出规律性认识用以指导今后工作的事务性文书。 A、正确 B、错误

单项选择题 在死亡和濒临死亡阶段，老年人常会承受身心方面的双重痛苦。社会工作者要了解临终者可能会有的恐惧、绝望、压抑等心理反应，了解临终者对于治疗的愿望，为老年人提供（ ）服务，使老年人能有尊严地离世。