例如在一篇短文中有这样一句话,The old man went up to the boys and asks them what it was happening.句中的第一个错误是并列的时态不一致,应将asks改为asked。第二个错误是多一个词“it”。这类错误要仔细观察句子结构,进行语法分析才能发现。一些逻辑上的错误,从语法角度来看是正确的,但通过上下文的逻辑关系来看,就会发现错误。
例如:People in industrial countries can expect to live for twice as long as people who lived a few years ago. Therefore, there are still some countries where people have shorter lives. 句中Therefore 改为 However 。
上文说:在工业发达国家人们的寿命可能会比几百年前长两倍;下文说:还有一些国家人们的寿命就短多了。这是一种明显的转折关系,,而非因果关系,所能不能用 therefore。虽然 but 也能表示转折关系,但后面有一个逗号,只能用 however。