Text: Passengers who fly between Europe and North America often notice that the journey east is shorter than the journey west, sometimes by more than an hour. The aircraft and the distance are the same, so the difference comes from the air itself. At the altitudes where airliners cruise, narrow bands of strong wind called jet streams flow from west to east. Their speed can exceed 200 kilometres per hour. An aircraft flying with a jet stream gains a powerful tailwind, while one flying against it must push through a headwind. Flight planners therefore do not simply choose the shortest line on a map. Every day they calculate routes that make use of the jet stream when flying east and avoid its strongest parts when flying west. Because the position of the jet stream shifts from day to day, two flights on the same route can follow quite different tracks. A slightly longer path can still save time and fuel. Question: Which conclusion is supported by the text?

Text: When a mid-sized logistics company decided to test a four-day working week, many managers expected productivity to fall. Employees kept their full salary but worked one day less, on the condition that the same amount of work was completed. After six months, the results surprised the sceptics. Delivery times had not changed, and the number of sick days had dropped noticeably. Staff reported that they planned their days more carefully and spent less time in meetings that had no clear purpose. Not everything went smoothly, however. The customer service team struggled, because customers still expected someone to answer the phone five days a week. The company solved this by creating a rota, so that each team member took a different day off. The trial did not prove that a shorter week suits every organisation, but it showed that the number of hours worked is not always the best measure of what people achieve. Question: What is the function of the sentence 'Not everything went smoothly, however.'?