1. (10 points) $2012.25 \times 2013.75-2010.25 \times 2015.75=(\quad)$
A. 5
B. 6
C. 7
D. 8
【Analysis】Regarding 2012.25 as $2010.25+2$ and 2015.75 as $2013.75+2$, the original expression becomes $(2010.25+2) \times 2013.75-2010.25 \times(2013.75+2)$, which further simplifies to $2 \times 2013.75-2010.25 \times 2$, and then the distributive property of multiplication can be used to simplify it.

【Solution】Solution: $2012.25 \times 2013.75-2010.25 \times 2015.75$,
$$
\begin{array}{l}
=(2010.25+2) \times 2013.75-2010.25 \times(2013.75+2), \\
=2010.25 \times 2013.75+2 \times 2013.75-2010.25 \times 2013.75-2010.25 \times 2, \\
=2 \times 2013.75-2010.25 \times 2, \\
=(2013.75-2010.25) \times 2, \\
=3.5 \times 2, \\
=7
\end{array}
$$

Therefore, the answer is: $C$.