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在英文中句群常呈总分结构，如下例：

A 31 year old woman with no medical history of note presented with bilateral lower leg pain on running. The pain was absent when she started running; gradually built after the first kilometer, forcing her to stop; then resolved shortly after stopping. 来源：BMJ

We did a systematic review and meta-analysis to estimate the efficacy of steroids for the prevention of mortality in all forms of tuberculosis, and to quantify heterogeneity in this outcome between affected organ systems. We searched the Cochrane Infectious Diseases Group trials register, the Cochrane Central Register of Controlled Trials, Medline, Embase, and Literatura Latino-Americana e do Caribe em Ciências da Saúde (LILACS) for studies published up to Sept 6, 2012, and checked reference lists of included studies and relevant reviews. We included all trials in people with tuberculosis in any organ system, with tuberculosis defined clinically or microbiologically. There were no restrictions by age, comorbidity, publication language, or type, dose, or duration of steroid treatment. We used the Mantel-Haenszel method to summarise mortality across trials. 来源：Lancet

论文中一段就阐述一个主题，一段话最理想的情况是3-4句话，最好不要超过5句话，段首是lead sentence，其余是subsequent sentences，针对lead sentences进行详细说明、举例子、补充说明，等等。在写英文论文时注意这一特点，写出的文章逻辑才会更加清晰，读起来更加舒服一些。