Viết lại câu sao cho hoàn chỉnh

1. Unless we protect the enviroment, we will destroy ourselves ⇒ If...... 2. Unless she is more hard- working, she will get low marks ⇒ If...... 3. Unless he listens to his parents, he will fail ⇒ If...... 4. They began watching the movie one hour ago ⇒ They have............. 5. He last cried ten years ago ⇒ He has....