他完成了艰苦的训练。

He finished a ___tough workout.

这个项目很艰难，但我们最终完成了。

The project was really ___tough, but we finished it in the end.

这些士兵经过严格的训练，变得非常坚韧。

These soldiers became very ___tough after rigorous training.

这位教练以严格的训练方式而闻名。

The coach is known for his ___tough training methods.

这块肉太老了，我牙齿都快咬不动了。

The meat is so ___tough that my teeth can hardly chew it.