词形变换：选择方框里的词的正确形式填空，每词只用一次。（10分） discover  do  surprise  burn  hold  add  heavy  find  use  observe 1. We ________ a science experiment in class tomorrow. 2. Do you know who ________ America? 3. They will show us a ________ experiment in class. 4. I have nothing ________ to my letter. 5. Air is ________ than we think. 6. The force is strong enough ________ the water. 7. I will ask the class to make ________ and guess what will happen. 8. An Easter egg hunt is a game for ________ eggs. 9. To make a candle ________, you “light” it. 10. When the candle stops burning, it ________ up all the oxygen in the air.