Odpowiedź :
a. My father has been to London.
b. My parents have been to New York.
c. I have studied English since I was 3 years old.
d. Marta has worked at Fontarron school for 5 years.
e. I haven't visited my grandparents since last month.
f. Coronavirus has killed many people.
'have' używamy do osób: I, you, we, they
'has' używamy do osób: he, she, it