雅思作文中免不了要考虑句子多样性。在句子中常会有逻辑主语来开头。所谓的逻辑主语就是一些非谓语动词的真正主语。这些非谓语动词，譬如说动名词、不定式，还有现在分词和过去分词，很多同学都在用，但是很多时候忘记真正的主语。 1 不定式to do, in order to do something In order to attract visitors, historic buildings should be maintained. 错误的原因：历史建筑是没有生命的，不可能有“in order to” 正确的句子：In order to attract visitors, city councils should maintain historicbuildings. 2 when, while, before, after 等连词引导的现在分词 例句：When communicating with others, patience is important. 错误的原因：communicating这个分词的主语是人，不可能是patient 正确的句子：when communicating with others, one should show patience. 3 by+doing 例句：By setting rules, children can reduce behavioural problems. 错误的原因：setting rules的主语不是children 正确的句子：By setting rules, schools can reduce behavioural problems.