Which expression is equivalent to 19x − 6x + 2 and why?

15x, because 19x − 6x + 2 = 13x + 2 = 15x
11x, because 19x − 6x + 2 = 19x − 8x = 11x
2 + 13x, because (19x − 6x) + 2 = 13x + 2 = 2 + 13x
2 − 13x, because (19x − 6x) + 2 = −13x + 2 = 2 − 13x