12. Arrange the odd positive integers $1,3,5,7, \cdots$ into five columns, as shown in the table. If the pattern continues, the column in which 2001 is located, counting from the left, is ( ).
\begin{tabular}{lllll} 
& 1 & 3 & 5 & 7 \\
15 & 13 & 11 & 9 & \\
& 17 & 19 & 21 & 23 \\
31 & 29 & 27 & 25 &
\end{tabular}
A. First column
B. Second column
C. Third column
D. Fourth column
12. The numbers in the first column, when divided by 16, leave a remainder of 5 or 9, and the numbers in the fifth column, when divided by 16, leave a remainder of 7. Since 2001, when divided by 16, leaves a remainder of 1, the answer is B.