重点讲解：
1. focus on 集中（注意力）；关注；
例句：Throughout the exercise, focus on keeping your abs tight.
整个锻炼过程中，注意要紧绷腹肌。
2. participate in 参与；参加；
例句：They expected him to participate in the ceremony.
他们希望他参加典礼。
3. complain about 抱怨；发牢骚；
例句：The neighbours always complain about the noise.
邻居们总是抱怨噪音问题。
4. learn from 向……学习；
例句：There is a great deal to learn from Hal's expert approach.
从哈尔熟练的方法中可以学到很多。
5. no doubt 无疑地；必定；
例句：She's a very sweet woman, as you no doubt know by now.
她是一个非常温柔的女人，你现在肯定知道了。
