rajatvmittal wrote:In the feudal system, nobles typically hired knights to prepare for the possibility of battle. When battles occurred, nobles led their knights either in invading surrounding lands, or in defending against the invasion of their lands from surrounding nobles. In training for success in battle, knights, unlike nobles, planned strategies that did not depend on an offensive or defensive position. Knights, then, did not regard the location of battle as relevant to success.
Which of the following, if true, would most seriously weaken the conclusion above?
In making battle plans, knights, unlike nobles, had no knowledge of whether they would be invading or defending land.
In the feudal system, it was clear when a battle was successful because the winners received land from the losers.
Knights were as likely to be successful in an offensive battle as were nobles.
Nobles made decisions about the location of battle based on prior movements of nobles from surrounding lands.
Knights planned strategies for success in battle that depended on the ability of their nobles to provide equipment.
Our aim here is to weaken the argument and the best way to weaken the argument is by attacking the central assumption of the argument.
Now in this argument author is saying that
Knights, then, did not regard the location of battle as relevant to success.
Now here author is assuming that knights knew about the location and they intentionally didn't regard the location of the battle as relevant to success. What if Knights didn't even know about the location then the assumption will be broken and the argument will fall apart.
Now a simple analogy for this argument would be something like this:
John walks to his work everyday even though his work is 5Km away from his home. So John likes walking. Now in the above simple argument author is assuming that john have other alternative such as car or public transport of something. If we have to weaken the above argument we can say "what if john doesn't have a car or any other sort of medium to travel". Then authors argument will be weaken to some extent. May be John doesn't like to walk but he doesn't have any other choice but to walk.
I hope this helps.
In the original sentence option D doesn't weaken the argument. It basically doesn't do anything atall. It just adds more info for General knowledge I believe

because author is making conclusion about knights and option D talks about Nobles.