1 . Continued trade in these products is a threat to the s______ of the species. (n. the state of continuing to live or exist, often despite difficulty or danger) (根据首字母单词拼写)

2 . His childhood dream to take an a ________ trip to space has been fulfilled. He said in an interview that it was full of new, exciting and dangerous experiences. (根据首字母单词拼写)

3 . Built for the 2008 Beijing Olympics, Beijing National S________, or Bird’s Nest, is a truly stunning piece of architecture. (根据首字母单词拼写)

4 . Xiao Ming would like to w________ (挥手) hands to show his delight of completing the race of 42.195 kilometers in Beijing Marathon on November 6^th in 2022. (根据中英文提示填空)