硬皮的

例句：

1. 1. The old tree has a hard, knotty bark.
   这棵老树有坚硬、多节的树皮。
2. 2. The new car is very hard to start.
   新车很难启动。
3. 3. The rocks are hard and unyielding.
   岩石坚硬且不可弯曲。