6. (10 points) Choose several numbers from $1, 2, 3, \cdots, 7$ such that the sum of the even numbers equals the sum of the odd numbers. The number of ways to do this is ( ) .
A. 6
B. 7
C. 8
D. 9
【Analysis】Identify which of the 7 natural numbers $1,2,3, \cdots, 7$ are odd and which are even, list the equations where the sum of the even numbers equals the sum of the odd numbers, and solve accordingly.

【Solution】Solution: Among $1, 2, 3, 4, 5, 6, 7$, $1, 3, 5, 7$ are odd numbers, and $2, 4, 6$ are even numbers,
$$
\begin{array}{l}
1+3=4 \\
1+5=6 \\
3+7=4+6 \\
3+5=2+6 \\
1+7=2+6 \\
1+5=2+4 \\
5+7=2+4+6
\end{array}
$$

There are 7 in total.
Therefore, the answer is: B.