891 - Logical Reasoning

Question: Our work proves to be very successful. In the past three years, each of our five clients has experienced the fastest growth of sales in their history. Therefore, if your company wants to increase sales, do not hesitate to call Sigma & Max, since we are the solution.
Which of the following, if true, most seriously jeopardizes the validity of the argument by the speaker above?

1. Most of the consultants at Sigma & Max hold MBA degrees.
2. Even without the help of Sigma & Max, the five clients of Sigma & Max will achieve the same growth rate in sale.
3. Sigma & Max is one of the five leading management consulting companies.
4. Sigma & Max uses an updated accounting approach to help companies to cut cost.
5. All of the five clients of Sigma & Max are doing business in financial industry.