英语翻译1,切勿践踏草地.{keep} 2,他谦虚的说他所作的不足挂齿.[worth] 3,上海博物馆对所有学生免费开放

1. keep off the grass!
2. he said humbly that what he did is not worth mentioning.
3. Shanghai museum is open to all students for free, which benefits the students a lot.
4. it was long before that