Q: What is a question about this article? If the question is unanswerable, say "unanswerable".
On the recovery side of the flight deck, the adaptation to the aircraft loadout is mirrored. Non-VTOL or conventional aircraft cannot decelerate on their own, and almost all carriers using them must have arrested-recovery systems (-BAR, e.g. CATOBAR or STOBAR) to recover their aircraft. Aircraft that are landing extend a tailhook that catches on arrestor wires stretched across the deck to bring themselves to a stop in a short distance. Post-WWII Royal Navy research on safer CATOBAR recovery eventually led to universal adoption of a landing area angled off axis to allow aircraft who missed the arresting wires to "bolt" and safely return to flight for another landing attempt rather than crashing into aircraft on the forward deck.
What do aircraft do when landing in order to stop on a long distance?
A: unanswerable

Q: What is a question about this article? If the question is unanswerable, say "unanswerable".
The official English name of the system is BeiDou Navigation Satellite System. It is named after the Big Dipper constellation, which is known in Chinese as Beidou. The name literally means "Northern Dipper", the name given by ancient Chinese astronomers to the seven brightest stars of the Ursa Major constellation. Historically, this set of stars was used in navigation to locate the North Star Polaris. As such, the name BeiDou also serves as a metaphor for the purpose of the satellite navigation system.
What was the Beidou constellation used for?
A: to locate the North Star Polaris

Q: What is a question about this article? If the question is unanswerable, say "unanswerable".
On March 31, 2010, the YouTube website launched a new design, with the aim of simplifying the interface and increasing the time users spend on the site. Google product manager Shiva Rajaraman commented: "We really felt like we needed to step back and remove the clutter." In May 2010, it was reported that YouTube was serving more than two billion videos a day, which it described as "nearly double the prime-time audience of all three major US television networks combined". In May 2011, YouTube reported in its company blog that the site was receiving more than three billion views per day. In January 2012, YouTube stated that the figure had increased to four billion videos streamed per day.
How many videos was YouTube serving per day in March 2010?
A: unanswerable

Q: What is a question about this article? If the question is unanswerable, say "unanswerable".
Growing scientific recognition of the role of private lands for endangered species recovery and the landmark 1981 court decision in Palila v. Hawaii Department of Land and Natural Resources both contributed to making Habitat Conservation Plans/ Incidental Take Permits "a major force for wildlife conservation and a major headache to the development community", wrote Robert D.Thornton in the 1991 Environmental Law article, Searching for Consensus and Predictability: Habitat Conservation Planning under the Endangered Species Act of 1973.
What did Thornton compare the scientific and legal advances to, from the viewpoint of the development community?
A:
a major headache