没有频繁的意思是，hard，意思是困难的、坚硬的，例如：
1、The substance polymerizes to form a hard plastic.这种物质聚合形成坚硬的塑料。
2、The cutters have very hard teeth made from special steel or from diamonds.刀具上有用特种钢或金钢石制造的非常坚硬的齿。
3、Granite is a very hard stone.花岗岩是一种很坚硬的石头。
没有频繁的意思是，hard，意思是困难的、坚硬的，例如：
1、The substance polymerizes to form a hard plastic.这种物质聚合形成坚硬的塑料。
2、The cutters have very hard teeth made from special steel or from diamonds.刀具上有用特种钢或金钢石制造的非常坚硬的齿。
3、Granite is a very hard stone.花岗岩是一种很坚硬的石头。
