1. Given the function $f(x)=\frac{4}{|x|+2}-1$ with the domain $[a, b]$, and the range $[0,1]$. Then the number of integer pairs $(a, b)$ that satisfy the condition is $(\quad)$.
(A)2
(B) 5
(C) 6
(D) infinitely many
-、1.B.
It is known that the graph of $f(x)$ is symmetric about the $y$-axis, and $f(x)$ is decreasing in the interval $[0,+\infty)$.
When $x \in \mathbf{R}$, $f(x)_{\max }=f(0)=1$.
Also, $f(-2)=f(2)=0$, then the integer pairs $(a, b)$ are
$$
(-2,0),(-2,1),(-2,2),(-1,2), (0,2)
$$