1. (2019·北京) 阅读下列短文，根据短文内容填空，在未给提示词的空白处仅填写1个适当的单词，在给出提示词的空白处用括号内所给词的正确形式填空。

    Earth Day, (mark)on 22 April, is an annual event aiming to raise public awareness about environmental protection. First celebrated 1970, the Day now includes events in more than 190 countries and regions (地区). No matter what you like to do, there is a way to get involved in various (activity) on Earth Day. You can plant a tree, make a meal with locally grown vegetables, or save power—the possibilities are endless.