SAT Newly Defined Functions

SAT® Math

For any numbers $m$ and $n$ , let $m \oplus n$ be defined as $m \oplus n= m-n+n^{2}$ . Which of the following will never be negative?

I. $a \oplus a$
II. $(a+b) \oplus b$
III. $(a+b) \oplus (a+b)$

(A) I only
(B) II only
(C) I and II only
(D) I and III only
(E) I, II, and III