1. Given in $\triangle A B C$, $\angle A=90^{\circ}, M$ is the midpoint of side $B C$, and point $N$ on the extension of $B C$ satisfies $A M \perp A N$. The incircle of $\triangle A B C$ touches sides $A B$ and $A C$ at points $E$ and $F$, respectively. $E F$ intersects $A N$ and $B C$ at points $P$ and $Q$. Then $P N - Q N$ ( ).
(A) greater than 0
(B) equal to 0
(C) less than 0
(D) uncertain
-1.B.
As shown in Figure 5.
From $A M \perp A N$, we know
$$
\begin{aligned}
& \angle A N M=90^{\circ}-\angle A M N=90^{\circ}-\angle A M C \\
& =90^{\circ}-\left(180^{\circ}-2 \angle A C M\right) \\
& =2\left(\angle A C M-45^{\circ}\right) \\
= & 2(\angle A C M-\angle A F E) \\
=2( & \angle A C M-\angle C F Q)=2 \angle C Q F .
\end{aligned}
$$

Therefore, $\angle N P Q=\angle N Q P \Rightarrow P N=Q N$.