The Following Question(s) Refer to the Evolutionary Tree in Figure

The following question(s) refer to the evolutionary tree in Figure 22.4, whose horizontal axis represents time (present time is on the far right) and whose vertical axis represents morphological change. Figure 22.4
- Figure 22.6
A hybrid zone is indicated by plotting the frequency of the yellow-belly allele across the distance from the center of the hybrid zone. What is the gene frequency of the fire-bellied toad 20 km from the hybrid zone center?

A) 1
B) 0
C) 0.1
D) 10