1. 认识这个词（基础篇）
词：recur
英英释义：if something, especially something bad or unpleasant, recurs, it happens again
例句：If the cheating recurs, you will be expelled.
2. 体会这个词 （进阶篇）
“recur“是个不及物动词，意思是“反复出现”，因此可以用来替换 happen again。根据它的英英释义，它前面的主语经常是负向意义的名词。我们通过一些例子掌握它的用法。
我们常说的“下不为例”，也就是说同样的事情不要再发生了，这时就可以用 recur。比如如果再作弊，你将会被开除：
If the cheating recurs, you will be expelled.
我们常说如果只是治标不治本的话，存在的问题还会重复发生，就可以说：
Problems are likely to recur if you are just treating symptoms rather than getting to the bottom of the mess.
有些疾病在手术后也有复发的危险，我们就可以说：
Surgical success rates vary widely, so there is a danger that the illness may recur.
最后我们看几个《经济学人》中用到 recur 的例句，加深对这个词的印象：
1) Concerns about local balance-sheets in China have recurred over the past decade.
2) Widespread violence that had marred the last elections in 2008 had not so far recurred.
3) The plague recurred sporadically until the 19th century.
3. 从认识到会用（作业）
1）翻译下面的句子：
我们必须保证问题不会再次发生。
We must make sure that this problem does not recur.
造句
"Cheating is not allowed to recur in any examination." says the headteacher.
（参考翻译：We must make sure that the problem does not recur.）
