题目内容：

英语翻译
The frequent change of English teaching textbooks is to enlarge learners' vocabulary and improve their grammatical competence.
专业一点，因为这个问题我要写在试卷上的，

优质解答

The frequency of changing English teaching textbooks is to enlarge learners' vocabulary andimprove their grammatical competece.Textbook has a vital and positive part to play in the everyday job of tea...