It is answer A. because if you add (+) a negative (-) number to another negative number it becomes positive.
this strikes out answer B. which is a negative subtracting 1 from itself, which makes -2 instead of zero (0).
Because of this theorem, you know you will need to add (+) or subtract (—) a the same numbers to or from each other to have the number zero (0).
this theorem strikes out answer D. which is different numbers subtracting from each other.
<u>So the answer is A. because it is the same numbers adding (+) onto one another.</u>
