針對(duì)他們各人不同的需要挑選柔軟、軟硬適中或者堅(jiān)硬的床墊。Choose a soft, medium or firm mattress to suit their individual needs.恐龍峽谷中的化石都嵌在堅(jiān)硬的砂巖中。The fossils at Dinosaur Cove are embedded in hard sandstones.這種物質(zhì)聚合形成堅(jiān)硬的塑料。The substance polymerizes to ...