这种塑料经过特殊处理后变得更加耐用。

This plastic has been ___toughened to make it more durable.

艰苦的生活条件使他在情感上变得更加坚强。

The harsh living conditions ___toughened him up emotionally.

学校加重了对考试作弊的处罚。

The school has ___toughened the penalties for cheating on exams.