3. (2005 Liaoning Province College Entrance Examination for Science) Given the graph of the function $y=f(x)$ in the following figures, and for any $a_{1} \in$ $(0,1)$, the sequence $\left\{a_{n}\right\}$ obtained by the relation $a_{n+1}=f\left(a_{n}\right)$ satisfies $a_{n+1}>a_{n}\left(n \in \mathbf{N}^{+}\right)$, then the graph of the function is ( )
A.
B.
C.
D.
3. From $a_{n+1}=f\left(a_{n}\right), a_{n+1}>a_{n}$, we get $f\left(a_{n}\right)>a_{n}$, which means $f(x)>x$. Therefore, the graph of $y=f(x)$ is above the line $y=x$, so the answer is A.