Answer
$\mathrm{D} < \mathrm{C} < \mathrm{B} < \mathrm{A}$
Work Step by Step
By Newton's second law, the impulse delivered to an object is equal to the change in its momenta:
$\vec{\mathrm{I}}=\vec{\mathrm{F}}_{\mathrm{a}\mathrm{v}}\Delta t=\Delta\vec{\mathrm{p}}\qquad $9-6
----------
$\vec{\mathrm{I}}_{A}=F\Delta t$
$\displaystyle \vec{\mathrm{I}}_{B}=(2F)(\frac{\Delta t}{3})=\frac{2}{3}F\Delta t$
$\displaystyle \vec{\mathrm{I}}_{C}=\frac{1}{2}F\Delta t$
$\displaystyle \vec{\mathrm{I}}_{D}=\frac{1}{10}F\Delta t$
From least to greatest impulses, the forces are ranked
$\mathrm{D} < \mathrm{C} < \mathrm{B} < \mathrm{A}$.
