Language competence in various communicative activities in L2 largely depends on the learners' size of vocabulary. The target vocabulary of adult L2 learners should be between 2,000 high frequency words (a critical threshold) and 10,000 word families (for comprehension of university texts). For a TOEIC test, the threshold is estimated to be…

Problem Statement: Students may behave differently from each other during the learning process. While some of them struggle to conceive the subject with all respects (the deep studying approach), the others just memorize it without any effort to comprehend (the surface studying approach). Today, students usually learn the strategies on their own…