8. In the plane region $\{(x, y)|| x| \leqslant 1| y \mid, \leqslant 1\}$, it is always true that $a x - 2 b y \leqslant 2$. Then the area of the plane region formed by the moving point $P(a, b)$ is ( ).
(A) 4
(B) 8
(C) 16
(D) 32
8. A.

The plane region $\{(x, y)|| x| \leqslant 1, | y | \leqslant 1\}$ has four boundary points $(-1,-1),(-1,1),(1,-1),(1,1)$ that satisfy $a x - 2 b y \leqslant 2$, which gives us
$$
\begin{array}{l}
a + 2 b \leqslant 2, a - 2 b \leqslant 2, \\
-a - 2 b \leqslant 2, -a + 2 b \leqslant 2 .
\end{array}
$$

From this, the area of the plane region formed by the moving point $P(a, b)$ is 4.