For homework, I would recommend you to play these games. The grammar structures that they deal with will be present in your Trinity Exam.

Enjoy them!

http://www.marks-english-school.com/games/g_presperf.html

http://learnenglish.britishcouncil.org/en/grammar-exercises/just-yet-still-already

 http://learnenglish.britishcouncil.org/en/grammar-exercises/present-perfect

http://www.eclecticenglish.com/grammar/PresentPerfect1D.html