Data Sufficiency

Is d negative?

(2) e + d = -12
(2) e - d < -12

C, Both statements together are sufficient.

Stmt 1:
e + d = -12

e = -13, d =1 works
So does, e = -11 and d = -1.
Not sufficient.

Stmt 2:
e - d < -12

e = 1, d = 14 works
e = -15, d = -1 works.

Combined.

Substitute for e in the inequality from the given equation.
e + d = -12 ==> e = -d -12

-d - 12 -d < -12. can be solved to get d's sign.

Thanks the OA is C

But I have a question if we continue by substitution method for C then again 'd' can be
-ve i.e. -25 - (-12) < -12 or
+ve i.e. -1 - (+12) < -12

So I thought the answer is E, how do we correctly make a decision here?