Noun
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the blood group whose red cells carry neither the A nor B antigens
"people with type O blood are universal donors"
- type o - group o -
the 15th letter of the Roman alphabet
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a nonmetallic bivalent element that is normally a colorless odorless tasteless nonflammable diatomic gas
constitutes 21 percent of the atmosphere by volume
the most abundant element in the earth's crust
- atomic number 8