The correct answer is A.
h is the independent variable. The rate at which she is hiking is 2.5 km/hr. The dependent variable, h(x), is equal to 12 for a certain h.
[tex]h(x) = 2.5h + 4[/tex]
[tex]12 = 2.5h + 4[/tex]
[tex]8 = 2.5h[/tex]
[tex]h=3.2[/tex] hours
