Option D isn't fully seen in your picture but if you're adding together the units that are in the same position within the brackets, that's your answer.
1 + (- 2) is -1. - 4 + 6 is 2. 3 + (- 2) is 1. 5 + 4 is 9.
So top left should be the - 1. Bottom left is 1. Top right is 2. Bottom right is 9.