这种钢材的韧性使其能够承受巨大的压力。

The ___toughness of this steel allows it to withstand tremendous pressure.

士兵们在训练中表现出的坚韧让他们能够适应恶劣的环境。

The soldiers' ___toughness during training allowed them to adapt to harsh conditions.

老师以严格著称，但学生们都理解这种严厉是为了他们好。

The teacher is known for her ___toughness, but students understand it's for their own good.