“坚硬的”用英语怎么说？

针对他们各人不同的需要挑选柔软、软硬适中或者坚硬的床垫。Choose a soft, medium or firm mattress to suit their individual needs.恐龙峡谷中的化石都嵌在坚硬的砂岩中。The fossils at Dinosaur Cove are embedded in hard sandstones.这种物质聚合形成坚硬的塑料。The substance polymerizes to ...