Correct Answer: EASY
Explanation: after “during” needs a noun: transparent, while
Translating the passage:
The relationship between teachers and students in the US is less formal than in other countries. American students do not need to get up when the teacher enters the classroom. Students are encouraged to ask questions during class time, to enter the teacher’s room to request additional help, and to be called if absent. Most teachers allow their students to enter class late or leave class earlier if necessary. Although not formal, students are expected to be polite to teachers and polite to friends.
When students want to ask a question, they usually raise one hand and wait to be called. When taking the test, talking in class is not only impolite, but also very risky. Because most American teachers consider talking during test hours as cheating.