【单选题】

{{I}} Questions 11-13 are based on the following passage. You now have 15 seconds to read the questions 11-13.{{/I}} Why do summer schools arrange visits and other activities for the students

A、To attract more students.
B．To make the courses suitable for students of all levels.
C．To let the students have a good rest.
D．To help everyone to make new friends, have fun and improve theirEnglish.