Bird wiki:
>For other uses, see Bird (disambiguation). Many - see section below. Birds are bipedal, warm-blooded, egg-laying vertebrates characterized primarily by feathers, forelimbs modified as wings, and hollow bones. Birds range in size from the tiny hummingbirds to the huge Ostrich and Emu. Depending on taxonomic viewpoint, there are about 8,800â10,200 living bird species (plus about 120â130 that have become extinct in the span of human history) in the world, making them the most diverse class of terrestrial vertebrates.
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Combination wiki:
binatorics">combinatorial mathematics, a combination of members of a set is a subset. A k-combination is a subset of S with k elements. The order of listing the elements is not important in combinations: two lists with the same elements in different orders are considered to be the same combination. The number of k-combinations or k-subsets of set with n elements is the binomial coefficient "n choose k", written as nCk, nCk or as
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