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WILL MARK BRAINLIEST ANSWER!!!!!

The table below shows the half-life of an element:


Half-Life Data
Element Half-Life
Uranium-235 700 million years


Scientists have found that the uranium-235 content of an unknown prehistoric sample was reduced to one-half. What best describes the identity of the sample?
A. A rock that formed 700 million years ago
B. A rock that formed 1,400 million years ago
C. An organism that died 700 million years ago
D. An organism that died 1,400 million years ago