Given the relation R(A,B,C,D) with FD's A - B; A - C; C-D, What is the closure of attribute A with respect to the functional dependencies?
1) {A}
2) {A,B,C}
3) All the attributes dependent on the primary key (including C: {A,B,C,D} the primary key, A, itself)
4) {B,C}