参考答案

正确答案：
The principle for selecting vocabulary is that an essential core vocabulary is covered. Learners should learn the most frequently used words, about 2,000 common core words. The items of grammar are graded following the principle that simple forms should be taught before complex ones. And grammar should be taught inductively and students learn to use a few patterns at a time. These patterns should be interesting and be presented in a carefully ordered sequence.