f(x)=1/2x^2-2x+20
h = -b/2a is the axis of symmetry
h = - (-2)/ (2 * 1/2)
h = 2 /1
the axis of symmetry is x=2
D.
The flight of the bird is symmetric about the line x = 2 feet, which indicates that the bird is at the same height when it is horizontally 1 foot and 3 feet away from where it began its flight.