The 22 students of the course of History of Italian Opera must write a short paper about at least two composers, they have a better grade, if they choose to write a paper about one more composer. among the students 17 choose Verdi, 15 choose Rossini, 15 Donizetti. how many students have chosen to write three papers?
a) 2 students
b) it is impossible to answer this question
c) 3 students
d) nobody has chosen three composers
e) 15 students