Given the functions f(x) = x2 + 6x − 1, g(x) = –x2 + 2, and h(x) = 2x2 − 4x + 3, rank them from least to greatest based on their axis of symmetry.
a. f(x), g(x), h(x)
b. h(x), g(x), f(x)
c. g(x), h(x), f(x)
d. h(x), f(x), g(x)