医生推荐特定的练习来加强膝盖周围的肌肉。

Doctors recommend specific exercises to ___strengthen the muscles around the knee.

政府计划加强法规以保护当地环境。

The government plans to ___strengthen regulations to protect the local environment.

随着她获得更多经验，她的信心明显增强了。

As she gained more experience, her confidence ___strengthened noticeably.