Why does the author mention so many events in Paragraph 12？
A. To show that migration exerts a great impact on population change.
B. To illustrate that migration contributes to mankind"s progress.
C. To reveal that migration is generally associated with great occurence.
D. To explain that migration may not be accompanied by human conflicts.
A．Business courses have become popular.B．The school only offers business courses.
A. Business courses have become popular.
B. The school only offers business courses.
C. The business school has a new program.
D. The school has just started to offer business courses.
What can be inferred about the gap between teachers and undergraduates？
A. It will not exist in future.
B. It would never disappear.
C. It may practically be avoided.
D. It should be bridged.
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