We know that the pole is perpendicular to the ground
And that the length of the pole is 20 feet tall, and the base is 15 feet
Now, the guy wire is a wire that provides support to the pole by connecting the top of the pole to the ground
So this represents a right angled triangle (refer image), and the hypotenuse is the length of the guy wire
Using Pythagoras theorem, we can find out the length of the hypotenuse
⇒ Hypotenuse² = Perpendicular² + Base²
⇒ Hypotenuse² = 20² + 15²
⇒ Hypotenuse² = 400+225
⇒ Hypotenuse² = 625
⇒ Hypotenuse = √625
⇒ Hypotenuse = 25
Hence, the correct option is B 25 ft.