82. How long does a jacket like this last me?(这要看你多长时间穿一次).
【参考答案】This depends on how often you wear it.
83. The theory he advanced has proved (对许多多传统概念是一种挑战).
【参考答案】
(to be )a challenge to many traditional notions / concepts.
84. The manager  (本可以亲自参加会议), but he was called away for some urgent business abroad.
【参考答案】
should have been able to attend the meeting in person.
85. Both research and practical experience have shown that a (均衡的饮食对健康是必不可少的).
【参考答案】
a balanced diet is necessary is good health.
86. Much (我感到遗憾), I was unable to finish the work on time.
【参考答案】
to my regret.