Explicação com vídeo: https://www.youtube.com/watch?v=6IilS4SEqyA
Link 1: https://www.ego4u.com/en/cram-up/grammar/simpas-preper/exercises
Link 2: http://speakspeak.com/english-grammar-exercises/intermediate/past-simple-or-present-perfect-3
Link 3: http://www.englisch-hilfen.de/en/exercises/tenses/simple_past_present_perfect4.htm