The relationship (15)_________ students and teachers is less formal in the USA than in other countries. American students do not stand up (16) ___________ their teachers enter the room. Students are encouraged to ask questions during the class, to stop in the teacher’s office for extra help, and to phone if they are absent. Most teachers (17) ___________ students to enter class late or leave early if necessary. Despite the lack of formality, students are still expected to be (18) ___________ to their teachers and fellow classmates. When students want to ask questions, they usually (19) ___________ a hand and wait to be called on. When a test is being given, talking to a classmate is not only rude but also risky. Most American teachers consider that students who are talking to each other (20) ___________ a test are cheating. 15.A. among B. both C. between D. from