— Exactly, _______they've learned a lot about grammar and known many words.
增加:在缺词处加一个漏字符号(∧),并在右边横线上写出该加的词。
删除:把多余的词用斜线(\)划掉,并在右边横线上写出该词,也用斜线划掉。
修改:在错的词下划一横线,并在右边横线上写出修改后的词。