Question: I know that the answer to the question "What happened in April of 1918?" is in "In February 1918, he was appointed Officer in Charge of Boys at the Royal Naval Air Service's training establishment at Cranwell. With the establishment of the Royal Air Force two months later and the transfer of Cranwell from Navy to Air Force control, he transferred from the Royal Navy to the Royal Air Force. He was appointed Officer Commanding Number 4 Squadron of the Boys' Wing at Cranwell until August 1918, before reporting to the RAF's Cadet School at St Leonards-on-Sea where he completed a fortnight's training and took command of a squadron on the Cadet Wing. He was the first member of the royal family to be certified as a fully qualified pilot. During the closing weeks of the war, he served on the staff of the RAF's Independent Air Force at its headquarters in Nancy, France. Following the disbanding of the Independent Air Force in November 1918, he remained on the Continent for two months as a staff officer with the Royal Air Force until posted back to Britain. He accompanied the Belgian monarch King Albert on his triumphal reentry into Brussels on 22 November. Prince Albert qualified as an RAF pilot on 31 July 1919 and gained a promotion to squadron leader on the following day.". Can you tell me what it is?
Answer: establishment of the Royal Air Force

Question: I know that the answer to the question "What aside from the sharpness of vision can aid in hunting prey?" is in "Many birds show plumage patterns in ultraviolet that are invisible to the human eye; some birds whose sexes appear similar to the naked eye are distinguished by the presence of ultraviolet reflective patches on their feathers. Male blue tits have an ultraviolet reflective crown patch which is displayed in courtship by posturing and raising of their nape feathers. Ultraviolet light is also used in foraging—kestrels have been shown to search for prey by detecting the UV reflective urine trail marks left on the ground by rodents. The eyelids of a bird are not used in blinking. Instead the eye is lubricated by the nictitating membrane, a third eyelid that moves horizontally. The nictitating membrane also covers the eye and acts as a contact lens in many aquatic birds. The bird retina has a fan shaped blood supply system called the pecten. Most birds cannot move their eyes, although there are exceptions, such as the great cormorant. Birds with eyes on the sides of their heads have a wide visual field, while birds with eyes on the front of their heads, such as owls, have binocular vision and can estimate the depth of field. The avian ear lacks external pinnae but is covered by feathers, although in some birds, such as the Asio, Bubo and Otus owls, these feathers form tufts which resemble ears. The inner ear has a cochlea, but it is not spiral as in mammals.". Can you tell me what it is?
Answer: Ultraviolet light is also used in foraging

Question: I know that the answer to the question "Which of the following is not a physicist: Clarke, Leibniz or Water?" is in "Standing out in Clarke's (and Newton's) response to Leibniz's arguments is the bucket argument: Water in a bucket, hung from a rope and set to spin, will start with a flat surface. As the water begins to spin in the bucket, the surface of the water will become concave. If the bucket is stopped, the water will continue to spin, and while the spin continues, the surface will remain concave. The concave surface is apparently not the result of the interaction of the bucket and the water, since the surface is flat when the bucket first starts to spin, it becomes concave as the water starts to spin, and it remains concave as the bucket stops.". Can you tell me what it is?
Answer:
Water