To become a citizen of the United States, you must
A. pass an English and government test.
B. file a request form in a federal court.
C. have lived in the United States for at
least six months.
ОО
D. be at least 21
years
old.

Explanation:

To  become a U.S. citizen you must meet the following requirements:

1) You must be 18 years of age or older.

2) You must have authorization to live and work in the U.S. on a permanent basis (informally known as a green card) for at least five years (or three years, if married to a United States citizen).

offline recommendation systems option b

because recommendation systems produce a list of two ways

1. through collaborative filtering

or

2. through content-based filtering