The upper interior surface of a room is called the ceiling. The upper exterior surface of a building is called the roof.
A tall apartment building has many ceilings inside it, because each level has its own ceiling - but it only has one roof, at the very top.
Fact
There are four main Blood types: A, B, AB and O and each Blood type is either Rh positive or negative. Blood types in the US Type O positive 38.4%, O negative 7.7%, A positive 32.3%, A negative 6.5%, B positive 9.4%, B negative 1.7%, AB positive 3.2%, AB negative 0.7%
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