用方框中所给单词的适当形式填空。 pass pollution he waste develop 1. Air _______ is the most serious problem at the moment. 2. As we know, China is still a _______ country in the world. 3. Bruce succeeded in _______ the English exam. 4. Water is becoming less and less, so you aren't supposed to _______ every drop of water. 5. My grandpa has seen the changes in Lianjiang _______.