Answer
The correct answer is (a). The graph is a straight line through the origin.
Work Step by Step
Hooke's law applies to DNA $F=kx$ and power at constant speed is $P=Fv$ and $x=vt$.
So
$P= Fv=kxv=kv^2t$.
$k$ and $v$ are constants so the power is proportional to the time. The graph should be a straight line.
