The Graphs Shown Show the Magnitude F of the Force

The graphs shown show the magnitude F of the force exerted by a spring as a function of the distance x the spring has been stretched. For which one of the graphs does the spring obey Hooke's Law?
a)

b)

c)

d)

e)

A) Graph a
B) Graph b
C) Graph c
D) Graph d
E) Graph e