Which of the following people can apply for naturalization?
a. a lawful permanent resident who has lived in the U.S. for 36 months
b. a lawful permanent resident who has lived in the U.S. for 18 months
c. a lawful permanent resident who has lived in the U.S. for 48 months
d. a lawful permanent resident who has lived in the U.S. for 60 months