Answer: Choice B and D are both correct.
Explanation:
The expression has two adjacent negative signs in the middle. The two negative signs are to be multiplied, which then produces one positive sign.
Choice B is therefore correct because the expression becomes 6+6 which is 6 to the right of the number line where the numbers are increasing.
Choice D is also equally correct because the addition of 6 to 6 equals 12(6+6 = 12).