Please don't give link and give proper reason of each step in your solution with suitable figure ( correct option is a)

Dear Student,
Given, mass of the knife edge = 200g = 0.2kg; dropped from a height h = 5m; penetrates the cardboard upto a depth, d = 2m
Therefore, Total energy loss in potential energy = mgh + mgd = mg(h+d), g = acceleration due to gravity = 10m/s².
Total work done by the resistance = F.d, where, F = retarding force due to the resistance of the cardboard
From work-energy theorem:
F.d = mgh + mgd
​$$\begin{gathered} F\times 2 = 0.2\times 10\times \left(5+2\right) \\ F = 7N \\ Ans \left(a\right) \end{gathered}$$

Regards,