2. (2003 Anhui Province Competition Question) Definition: $A-B=\{x \mid x \in A$ and $x \notin B\}$. If $M=\left\{x \mid 1 \leqslant x \leqslant 2002, x \in \mathbf{N}_{+}\right\}, N=$ $\left\{y \mid 2 \leqslant y \leqslant 2003, y \in \mathbf{N}_{+}\right\}$, then $N-M$ equals ( ).
A. $M$
B. $N$
C. $\{1\}$
D. $\{2003\}$
2. Choose I. Reason: $N-M=\{x \mid x \in \mathbf{N}$ and $x \notin M\}=\{2003\}$.