用代词时，检查指代关系是否清楚。
例1：
a) Sometimes teachers will inform students of the heavy burden theyhave to bear.
b) Sometimes a teacher will inform students of the heavy burden he has to bear.
分析：they 既可指代teachers, 也可指代 students，明显的是指代不清。其实只要把其中一个名词变成单数，用he和 they分别代不同的名词，就清楚了。因为 a teacher也可泛指所有教师。
例2：
a) Someone believes that the teacher's task is to give students knowledge, which may not be true.
b) Someone believes that the teacher's task is to give students knowledge, a notion which may not be true.
