I think you guys need to have more practice

Present Perfect exercises

I think you guys need to have more practice with the present perfect simple and continuous. Here are some links for a few online exercises:

Past Simple vs. Present Perfect
http://www.englishpage.com/verbpage/verbs5.htm

Present Perfect Simple
http://www.ego4u.com/en/cram-up/grammar/present-perfect-simple

Present Perfect Simple vs. Continuous
http://www.ego4u.com/en/cram-up/grammar/prepersim-preperpro