5. The three point sets on the plane are $M=\{(x, y) \mid | x|+| y |<1\}, N=\{(x, y) \mid$ $\left.\sqrt{\left(x-\frac{1}{2}\right)^{2}+\left(y+\frac{1}{2}\right)^{2}}+\sqrt{\left(x+\frac{1}{2}\right)^{2}+\left(y-\frac{1}{2}\right)^{2}}<2 \sqrt{2}\right\}, P=\{(x, y) \mid | x+y|<1, | x |<1$, $|y|<1\}$, then
A. $M \subseteq P \subseteq N$
B. $M \subseteq N \subseteq P$
C. $P \subseteq N \subseteq M$
D. A, B, C all hold
5. B Set $M$ represents the interior (excluding the boundary) of a square with vertices at $(0,1),(1,0),(-1,0),(0,-1)$. Set $N$ represents the interior (excluding the boundary) of an ellipse with foci at $\left(\frac{1}{2},-\frac{1}{2}\right),\left(-\frac{1}{2}, \frac{1}{2}\right)$ and a major axis length of $2 \sqrt{2}$. Set $P$ represents the interior (excluding the boundary) of a parallelogram with vertices at $(-1,2),(1,0),(-1,0),(1,-2)$. By plotting the corresponding figures in the Cartesian coordinate system, it is easy to see that $M \varsubsetneqq N \varsubsetneqq P$.