I. Multiple Choice Questions (10 points per question, full score 60 points. Among the four options for each question below, only one is correct. Please write the English letter representing the correct answer in the parentheses of each question.)
1. $2012.25 \times 2013.75-2010.25 \times 2015.75=($ ).
A. 5
B. 6
C. 7
D. 8
$$
\begin{aligned}
\text { Original expression } & =(2010.25+2) \times(2015.75-2)-2010.25 \times 2015.75 \\
& =2015.75 \times 2-2010.25 \times 2-4 \\
& =7
\end{aligned}
$$

The answer is $C$.