Find the Union of the Sets

Multiple Choice

Find the union of the sets.
-{-5, -2, 1, 4} ∪ {1, 4, 7}

A) {1, 4}
B) {1, 4, 7}
C) {-5, -2, 1, 4}
D) {-5, -2, 1, 4, 7}