well lets look at each
A. symetric property is if a=b then b=a
this is not the answer
B. aditive inverse is adding the inverse so
that would be x+(-x)=0 which is not this one
C. additive identity property, the identity stays the same if you add 0
so x+0=x
this is the answer
D. opposite of a sum property, this is adding a negative or
x-y=x+(-y)
the answer is C