Our work proves to be very successful. In the past three years, each

The author claims that this S&M company will provide solutions to increase sales. To support this claim, the author provides the details about its success with all five clients it served. So, basically the solutions S&M provide are sufficient condition here, and the increase in sales is the necessary result.

To weaken the validity of the argument, we may prove that the solutions are not sufficient to cause the increase in sales, or solutions do not necessary result in increased sales. Let's look at the options.

A - This information is not relevant. Whether the MBA education helps in finding solutions to increase sales is not mentioned.
B - Alright so this informs us that even without cause (applying solutions), the results exist. This information has to do something with causal relation. Let's hold on.
C - The information is almost like that in option A.
D - Cost cutting does not helps to increase sales. Not relevant at all.
E - The conclusion claims to increase sales for any company, not just finance company. So, this analogy is not valid here.

Hence, option B remains unchallenged by our analysis. Indeed, if the result exist even in the absence of the mentioned cause, then causal relation between them does not necessarily exists. Remember, to bring a result there may be multiple causes but the mentioned cause always have to be present to produce the mentioned result. Therefore, option B successfully weakens the argument.