Can someone answer. there is one problem. there is a picture. you!

SA=4pir^2
78.54km^2=SA
78.54=4pir^2
divide both sides by 4
19.635=pir^2
aprox pi=3.14 so divide both sides by 3.14
6.25318=r^2
sqrt both sides
2.50063=r
round
radius=2.5km

this question is flawed in that it gives the wrong units

answer is the option with 2.5 in it
2nd one

Letter c hope it