Question: Extract the answer to the question from the following context. Question: what is the last period in time mentioned? Context: After a lengthy period of formal racial segregation in the former Confederacy following the Reconstruction Era, and bans on interracial marriage in various parts of the country, more people are openly forming interracial unions. In addition, social conditions have changed and many multiracial people do not believe it is socially advantageous to try to "pass" as white. Diverse immigration has brought more mixed-race people into the United States, such as the large population of Hispanics identifying as mestizos. Since the 1980s, the United States has had a growing multiracial identity movement (cf. Loving Day). Because more Americans have insisted on being allowed to acknowledge their mixed racial origins, the 2000 census for the first time allowed residents to check more than one ethno-racial identity and thereby identify as multiracial. In 2008 Barack Obama was elected as the first multiracial President of the United States; he acknowledges both sides of his family and identifies as African American.
Answer: 2008

Question: Extract the answer to the question from the following context. Question: It was reported that 2 kids were killed in an accident, then which number will be inreased, 19.9% or 15.1%? Context: As of 2000[update], children and teenagers (0–19 years old) make up 15.1% of the population, while adults (20–64 years old) make up 65% and seniors (over 64 years old) make up 19.9%.
Answer: 19.9%

Question: Extract the answer to the question from the following context. Question: What is invisible to the human eye? Context: 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.
Answer:
ultraviolet