1. Let $A=\{1,2\}$, then the number of mappings from $A$ to $A$ that satisfy $f[f(x)]=f(x)$ is ( ).
(A) 1
(B) 2
(C) 3
(D) 4
-、1.C.
The functions are $f, g, h$, such that $f(1)=1, f(2)$ $=2 ; g(1)=g(2)=1 ; h(1)=h(2)=2$.