I think it is 1 because to find a mean, you add all together then divided it by the numbers that it has, they has 4 number -3, -2, -1, 2 in this problem.
Add all number together divided it by 4, you'll get -1, but the absolute of -1 will be 1.
(-3 + -2 + -1 + 2) ÷ 4 = -1