Although the Carbon 14 method of dating old objects is not foolproof , it is the best method available at present
A、whollyoperationalC
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The Native American interpreter Sacajawea was a valuable member of the Lewis and dark expedition in 1805.
The future survival of the bald eagle is still an important American ecological concern.
Urban renewal programs strive to upgrade areas that are becoming slums.
Whencarbonisaddedtoironintheproperproportions,theresultissteel.
Thefirstpaperwasmadefromthebarkofthemulberrytree.
