$G, A G>B G, C D=16, A E \perp C D$ at $E, B F \perp$ $C D$ at $F$. Then $A E-B F=$ ( ).
(A) 6
(B) 8
(C) 10
(I) 12
3. (D) .

Chord distance $O H=\sqrt{10^{2}-8^{2}}=6$. From $O H / / A E / / B F$ we get
$$
\frac{A E}{O H}=\frac{10+O G}{O G}, \frac{B F}{O H}=\frac{10-O G}{O G} .
$$

Subtracting the two equations yields
$$
A E-B F=2 O H=12 \text {. Therefore, the answer is (D). }
$$