Taking group photos is part of the graduation ceremony, it's like a tradition and Chinese take it seriously.
It is not mandatory, being absent wont cost you the certificate, but normally we wont miss it.
Traditionally, it's just a group of faculty members and students standing in front of the college library, therefore the photos are usually dull. But today's students add some creativity into this old tradition, making it much more interesting.
The girls in the photos are dancers.
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