在2008年五月十二日的汶川大地震中,许多孩子失去了父母和家园,全国人民伸出援助之手

在2008年五月十二日的汶川大地震中,许多孩子失去了父母和家园,全国人民伸出援助之手
用什么时态啊
文章给了个开头：As you know ,an earthquake happened on May 12th ,2008,many children in Wenchuan lost their parents and home.All the Chinese people have tried their
best to help them .You can also do something for them
根据以上,写一份倡议书