Barron’s ESL Proficiency Series: Prepositions provides comprehensive coverage of this most difficult topic in English grammar. The idiosyncratic nature of prepositions often makes them a barrier to achieving English language proficiency. Jean Yates offers clear explanations with lots of examples and opportunities to practice.  Content is organized into simple 15-minute units each of which has its own practice exercises. An answer key is included in the back of the book. The E