I (be)_________some places in the world but Singapore is the most beautiful country that I ever_________ (visit).
Have been to/ Have visited
The person that I admire the most in my life is my lecturer, Ms. Linh, who (do)___________a lot of research.
has done
My grandfather (collect)_____________stamps since he was 17 years old.
has collected
He (act)_______since he was a student in University of Stage and Cinematography.
has acted