毕竟煤炭矿床本身就是石化的泥炭沼泽，而泥炭的成份是腐烂的植物。当粘土泥浆逐渐硬化成页岩石，腐烂的植物则在上面留下了它们的印记。

Coal deposits, after all, are petrified peat swamps, and peat is made from decaying plants, which leave their imprints in mud and clay as it hardens into shale stone.

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大约从45岁左右初步，晶状体逐渐硬化、弹性下降，睫状体的功用也在减弱，然后出现老花眼。

From about the age of 45 or so initially, the lens gradually hardening, decreased flexibility, ciliary body function has been weakened, and onset of presbyopia.

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随着我们变老，血管逐渐硬化，这被认为增加高血压的风险。

As we age, our blood vessels get stiffer, and that's thought to increase the risk of high blood pressure.

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