重点讲解：
1. free time
空闲时间；
eg. He has a lot of free time he spends most of it in the garden.
他空闲时间很多——大都消磨在花园里了。
eg. People who use their free time well are usually healthy and happy.
善于利用空闲时间的人通常健康又快乐。
2. a bunch of
一伙，一群（人）；
eg. I shouldn't employ them — they're just a bunch of amateurs.
我不该雇用他们——简直是一群外行。
eg. Your friends are all just a bunch of nobodies.
你的朋友都不过是无名之辈。
3. once in a lifetime
千载难逢；一生一次；一生难得；
eg. It's definitely a once in a lifetime experience.
这绝对是一次毕生难忘的体验。
eg. "Participating in a race at the Olympics was a once-in-a-lifetime experience, " she said.
她说：“能参加奥运会比赛是人生中难得的经历。”
