Question

If A = {1, 2, 3,..., 10} R: A to A R = {(a, b): |a - b| is a multiple of 3} is an equivalence relation, then the equivalence class [1] is

A) {1,4,7}
B) {1,3,6,9)
C) {1,4,7,10)
D) {1,2,3,4}