1 . According to the report s_________ by researchers, about 23 percent of all annual carbon dioxide emissions are caused by the destruction of tropical forests. (根据首字母单词拼写)

2 . F________________(害怕) by smoke and noise, the child hides under a bed and is later found dead. (根据中英文提示单词拼写)

3 . Physical exercise will make a great difference. His health has improved a lot ________ (与……相比) with the past. （根据汉语提示单词拼写）

4 . The rocket is a________ (系，绑)to the spacecraft and is designed to drive the spacecraft towards Mars. （根据中英文提示填空）