Although the Carbon 14 method of dating old objects is not foolproof , it is the best method available at present
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TheNativeAmericaninterpreterSacajaweawasavaluablememberoftheLewisanddarkexpeditionin1805.
Solid geometry has enabled astronomers to calculate the positions of the heavenly bodies relative to one another.
The first important exposition in the United States was held in Philadelphia in 1876.
The megaphone(microphone) makes the voice sound louder because it points sound waves in one direction and keeps them from spreading out in all directions.
An oversight 遗漏 (miss, overslaugh) in proofreading often results in printed errors.