PTELook at the text below. In 35 seconds, you must read this text aloud as naturally and clearly as possible. You have 35 seconds to read aloud.

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Usually, age is determined by physical characteristics, such as teeth or bones. Great if you have a body. Researchers have tried unsuccessfully to use blood. But in this study, the scientists used immune cells called T-cells. T-cells recognize invaders through receptors that match molecules on bacteria, viruses, even tumors. The cellular activity that produces these receptors also produces a type of circular DNA molecule as a by-product.

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