For any two real numbers:

a + b = 1 if both a and b are positive or both a and b are negative.
a + b = -1 if one of the two numbers a and b is positive and the other negative.

What is (2 + 0) + (-5 + -6)?
A. a + b is zero if a is zero
B. a + b = b + a

A

the question can be answered by one of. the statements alone, but cannot be answered by using the other statement alone.

B

the question can be answered by using either statement alone.

C

the question can be answered by using both the statements together, but cannot be answered by using either statement alone.

D

the question cannot be answered even by using both statements together.