Step 1: In the forward bias region, the diode has a low resistance. In the reverse bias region, the diode has a very high resistance.
Step 2: From the I-V characteristic curve, we can see that the current in the forward bias is much higher than in the reverse bias. Therefore, the ratio of forward to reverse bias resistance is large, and the correct ratio is \( 10^6 \).
Final Answer:
\[
\boxed{10^6}
\]