变硬

例句：

1. 1.The paint on the wall has hardened over time.
   墙上的油漆随着时间的推移已经变硬了。
2. 2. The ground is getting hardened by the rain.
   地面因雨水而变硬了。
3. 3.The meat needs to be hardened before it can be cooked.
   肉需要先变硬才能烹饪。