The shadow of the 8-meter-high flagpole DE is: 12m,
The measured length of EG is 3m, and that of HF is1m..
∴GH= 12-3- 1=8(m)，
∴GM=MH=4m.
As shown in the figure, let the center of the bridge be O, connecting OM and OG.
Let the radius of the circle where the bridge is located be r,
MN = 2m，
∴OM=(r-2)m.
In Rt△OGM, from Pythagorean theorem:
∴OG2=OM2+42，
∴r2=(r-2)2+ 16，
Solution: r = 5.
A: The radius of the circle where the bridge is located is 5m.