If we ________ now to protect our mother river ---Li Jiang River , we ‘ll live to regret it.
So difficult _____it to live in an English-speaking country that I determined to learn English well.
So ____ that no fish can live in it.
---David has made great progress recently. ---_____, and ______.
Only in this way _____ progress in your English.
Only when the war was over _____ to his hometown.