Present Perfect Simple Vs. Past Simple

PRACTISE...

http://www.aulafacil.com/Ingejerc/Lecciones/Ejerc20.htm
http://www.englishpage.com/verbpage/verbs5.htm
http://www.usingenglish.com/quizzes/228.html
http://www.ego4u.com/en/cram-up/grammar/simpas-preper/exercises?ex04
http://www.perfect-english-grammar.com/past-simple-present-perfect-1.html
http://www.perfect-english-grammar.com/past-simple-present-perfect-2.html
http://web2.uvcs.uvic.ca/elc/studyzone/410/grammar/ppvpast1.htm
http://www.ego4u.com/en/cram-up/grammar/simpas-preper/exercises