5. On the plane, there is a set of points $M$ and seven different circles $C_{1}, C_{2}, \cdots, C_{7}$, where circle $C_{7}$ passes through exactly 7 points in $M$, circle $C_{6}$ passes through exactly 6 points in $M$, $\cdots$, circle $C_{1}$ passes through exactly 1 point in $M$. The minimum number of points in $M$ is
A. 11
B. 12
C. 21
D. 28
The intersection points of $C_{7}$ and $C_{6}$ can be at most 2, the intersection points of $C_{5}$ with $C_{7}$ and $C_{6}$ can be at most 4, so $C_{7}, C_{6}, C_{5}$ must contain at least $7+6+5-2-4=12$ points, meaning the number of points in $M$ is at least 12. Therefore, the answer is $B$.