$$
\begin{array}{c}
1.2013+2012-2011-2010+2009+2008- \\
2007-2006+\cdots+5+4-3-2+1=(\quad) .
\end{array}
$$
(A) 2013
(B) 2012
(C) 1
(D) 0
-,1. A.
It is evident that the symbols in the expression follow a periodic pattern.
Starting from the first number 2013, every four numbers form a group, resulting in 503 groups, with each group yielding a result of 4. The remaining number is 1, so the original expression $=4 \times 503+1=2013$.