natural hardness

例句：

1. 1. The natural beauty of the forest is breathtaking.
   森林的自然美景令人叹为观止。
2. 2.She was born in a small village with a natural charm.
   她出生在一个具有自然魅力的小村庄。
3. 3. The scientist discovered a new species that is naturally adapted to its environment.
   科学家发现了一种新物种，它自然适应了其环境。