EJERCICIOS REFUERZO Y NIVELACIÓN  8°

http://www.nspeak.com/newbasic/grammatica/presperfect.htm
http://www.english-grammar-lessons.com/presentperfect/exercise2.swf
http://www.english-grammar-lessons.com/presentperfect/exercise9.swf
http://www.english-4u.de/pres_perf_ex2.htm
http://www.montsemorales.com/gramatica/PresPerfJust.htm
http://eslus.com/LESSONS/GRAMMAR/PASSIVE/Gramc.htm
http://www.ego4u.com/en/cram-up/grammar/passive/exercises?simple-present-2
http://www.redcamelot.com/camelot/exercises/SEPT26/Grammar/Passive%20Voice/Exercise%202.htm