safe是形容词，名词词性，例如：
1. Employers should provide a safe working environment, as far as is reasonably practicable.只要条件许可，雇主就须提供安全的工作环境。
2.People must be satisfied that the treatment is safe.人们必须确信这种治疗方法是安全的。
3.We were glad she let us know she was safe.她告诉我们她平安无事，我们很高兴。