1．They worked day and night about three days （一切才恢复）to normal.(return)
2．I can’t imagine （他们多么激动）when they received these Christmas presents.(how)
3． （如果参加）eco-travel and you will find it will help you understand the importance of nature.(take)
4．Not （知道如何解决）the problem, he turned to his teacher for help. (work)
5．The doctor insisted that the patient （动手术）as soon as possible. (operate)
