Keratan
角质素
🗣️ 情景例句
Living conditions in the desert around Las Vegas are very harsh.
在拉斯韦加斯的周围的居住条件非常艰苦。
To lose a freind is the greatest of all loses.
失掉朋友是一切损失中最大的损失。
This decline in vigour with the passing of time is called ageing.
生命力随时间的流失而衰退叫做衰老。