Os alunos têm-se queixado por causa

Os alunos têm-se queixado por causa da falta de ar condicionado na sala de aula

Results (English) 1:

Students have been complaining because of the lack of air conditioning in the classroom

Results (English) 2:

Students have complained because of the lack of air conditioning in the classroom

Results (English) 3:

The students have complained about the lack of air conditioning in the room.