By the formula of torque balance we know that
[tex]\tau = r\times F[/tex]
here we know that
r = distance of force
F = applied force
so here we know that as we will take large edge knife then the distance of force will increase
due to this the torque will also increase in it so it is easy to pear it
So here we can say
[tex]F_{in}r_1 = F_{out}r_2[/tex]
[tex]F_{out} = \frac{r_1}{r_2} F_{in}[/tex]
so output force will increase in this case
So here the correct answer would be
b. the longer the knife, the stronger the output force