病毒隐性感染发生的原因是（）

[单选题]Passage1When it comes to airline travel, perhaps nothing has revolutionized the passenger experience more than airline apps. Indeed, they' re becoming so ubiquitous that more than 50 percent of U.S travelers have at least one airline app installed on their smart device, according to travel industry research firm Phocuswright.Maybe that's because apps make travel easier, and often are more functional than a kiosk or even an airline's own website. Passengers report that they' re often more quickly informed of a flight cancellation or gate change than an airline employee. Not all airline apps are created equal, but in general you can use an app to check in for a flight, change seats, and request and pay for an upgrade. Road warriors in particular appreciate mobile boarding passes and the ability to track their flights. Many airlines now offer free onboard streaming entertainment via apps. The Delta Air Lines app even allows users to track their bags, from check-in to carousel, while the Air France app lets passengers download magazines and newspapers from the airline's library 30 hours prior to departure.But what if you are traveling extensively on more than one airline? Global airline alliances have their own apps that allow you to view flights for all member airlines and their affiliates, including code share flights. In general, you can find flight schedules for all member airlines and track member airline flights. Airport information is available, as are details about local weather at the destination. Where's the nearest airport lounge? The app will locate it for you.The Sky Team airline alliance app goes a step further by letting its SkyPriority members (Sky Team Elite Plus members and customers with first and business-class tickets) find out exactly which SkyPriority services-including priority check in and baggage drop off, as well as access to priority security lanes and boarding lanes-are available at individual airports.You' ll find that some alliance app features are available through multiple channels of communication. For example, Sky Team members have formed their own online community by sharing traveler tricks and airport tips accessible through a variety of channels, including the app, Sky Team's website, Facebook page and a dedicated tips site. Sky Team's YouTube page features travel tips from regional celebrities.Just as airlines seem to have conquered social media, another method of communicating with travelers has just arrived. KLM Royal Dutch Airlines is the first carrier to sign up for Facebook's Messenger chat app. KLM flyers can automatically receive itineraries, flight updates, check-in notifications, boarding passes and rebook flights and communicate with customer service, all from Facebook Messenger. Messenger for Business was launched so that customers-in this case, passengers-can transact business over the messaging app in a single communication thread. Roughly 80 percent of passengers on planes traveling within the U.S. have the Messenger app installed on their smartphones, according to Facebook.Clearly, mobile apps and social media have transformed our digital lives. Airlines favor apps and other technologies because they get customers out of airport lines and off phone lines. Through their smart devices, travelers now have untethered access to travel information. A few quick taps can supply individuals with information never dreamed possible even a decade ago. And with more people using smartphones as their primary computing device, and as more people own cellphones globally, people expect technology-driven methods of communication and convenience to accelerate. Whether you' re high-tech or not, you must admit that having immediate access to the information you need sure beats getting a busy signal on a toll-free phone line.Which of the following reflects what the author intends to convey?

[单选题]著名的“洞穴喻”是谁提出的比喻（）

[问答题]国家旅游局根据国家开办出国旅游的指导方针，制定了中国公民自费出国旅游管理制度。除领队制度以外，其他几个制度分别是？

[单选题]测定金属离子的水样常用硝酸酸化至pH值为1～2，既可以防止重金属的水解沉淀，又可以防止金属在器壁表面上的吸附，同时在pH值为1～2的酸性介质中还能（）。

[单选题]《动车组列车服务质量规范》规定，对于应急处置预案，要求日常组织培训，定期组织演练，培训演练有记录，有结果，（）。

[单选题]鳞状细胞癌患者的皮损组织病理显示表皮内有大量的大小、形态不一的鳞状细胞团块，细胞排列紊乱，有异形性和病理性核分裂，瘤细胞间桥粒存在，并可见多数角株形成。首选的治疗为（）。

[判断题]证券发行、交易活动的当事人具有平等的法律地位，应当遵守自愿、有偿、诚实信用的原则。

[填空题]柱塞分泵每次泵出的油量取决于（）。

[单选题]根据中国证监会2007年3月对开放式基金认购费计算方法的统一规定，基金认购费的计算公式为()。

[单选题]关于喉的描述，正确的是（）