$26 \cdot 38$ On the plane, there are three point sets $M, N, P$:
$$
\begin{aligned}
M= & \{(x, y) \mid | x|+| y |<1\}, \\
N= & \left\{(x, y) \left\lvert\, \sqrt{\left(x-\frac{1}{2}\right)^{2}+\left(y+\frac{1}{2}\right)^{2}}\right.\right. \\
& \left.\quad+\sqrt{\left(x+\frac{1}{2}\right)^{2}+\left(y-\frac{1}{2}\right)^{2}}<2 \sqrt{2}\right\}, \\
P= & \{(x, y) \mid | x+y|<1, \quad| x|<1, \quad| y \mid<1\} .
\end{aligned}
$$

Then their relationship is
(A) $M \subset P \subset N$.
(B) $M \subset N \subset P$.
(C) $P \subset N \subset M$.
(D) None of (A), (B), (C) hold.
(China High School Mathematics League, 1988)