Dear student,
This kind of practice is for you to evaluate yourself. You can work with
a group of classmates in the library or alone at home. But usually working
alone is tough. So, it is much better to work with your partners. It is good, for
example, to complete the exam first and then correct among yourselves. This is
what teachers call Co-evaluation; it implies that some students can evaluate
the work of other classmates, like a previous practice, to provide feedback before
you take the real exam, quiz or test. 
I hope these exercises help you to truly
learn.
