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