B1
used to give extra information about something
Dictionary examples:
The exam, which was written in invisible ink, confused all the students. (0.0)
His new diet, which consisted only of ice cream, surprisingly worked well. (0.0)
My cat, which thinks it's a dog, often barks at the mailman. (0.0)
The book, which includes a map, gives you all the information you need about Budapest. (16.9)