Pearl - Wikipedia
A pearlis a hard object produced within the soft tissue (specifically the mantle ) of a living shelledmollusk . Ju...EtymologyDefinitionPhysical propertiesen.wikipedia.org/wiki/... - 百度快照 - 翻译此页
Pearl_百度百科
cast pearls before swine 把珍珠丢在猪面前; 明珠暗投; 对牛弹琴 He who would search for pearls must dive below. 欲寻珍珠就要潜到水里; 不入虎穴,焉...
