1.How long dose a jacket like this last me? _______________________ （这要看你多长时间穿一次）.
　　2. The theory he advanced has proved _________________ （对许多传统概念的一种挑战）.
　　3. The manager ___________________ （本可以亲自参加会议）,but he was called away for some urgent business abroad.
　　4. Both research and practical experience have shown that a __________________ （均衡的饮食对健康是必不可少的）.
　　5. Much ____________________ （我感到遗憾）, I was unable to finish the work on time.

　　答案与解析：
　　1.It depends on how often you wear it
　　2. (to be )a challenge to many traditional notions / concepts.
　　3.could have attended the meeting in person/by himself
　　4.a balanced diet is essential to health.
　　5.regretted as I felt