My two cents' worth through a combination of negation and discerning between a 'could be true' and a necessary statement to make the conclusion. We need to look for a potential link between the conclusion and the given premise:
Someone who accepted the reasoning in the advertisement above would be making which one of the following assumptions?
A. Without quality equipment, a tennis player cannot improve his game.
-Negating the statement, even if a tennis player can improve his game without quality equipment, this doesn't tell us if the author's argument is off - the product offered can still indeed help in raising the average amateur's tennis game.
So this does not go against the argument, nor is it necessary for the author to make the argument. B. The Spring-Strung racket will improve an amateur's game more than it will improve a professional's game.
It's not about whether the racket will improve an amateur's game more than that of a professional's - it's about whether it will even improve ANY of the amateur's game in the first place.
This is sort of a 2nd degree question that comes after "Can this racket even help me in the first place?" by asking "If so, by how much?"
Note that this isn't essential to making the conclusion as well. C. The quality of a person's tennis game is largely determined by the speed and force of his volley.
If the quality of a person's tennis game is NOT largely determined by the speed and force of his or her volley, then buying such a racket that does so would do little or no benefit to anyone's tennis game; this would make the author's argument fall apart.
E.g. if the quality of a person's tennis game is largely determined by how well one can anticipate the incoming serve of an opponent or how well one could throw the ball in the air before serving, then increasing the speed and power of your volley would be of little use in improving your tennis game.
This statement says that INDEED speed and power are key to raising your tennis game, and the author offers you just the right product for doing so. D. The Spring-Strung racket is superior to any other racket currently on the market.
Again, doesn't need to be superior to any other racket on the market - the author is not concluding or stating that his rackets are the best in the market.
He is saying that using his racket actually improves your game overnight by increasing the power and speed of your volleys. This is irrelevant. E. Lessons are not as effective at improving the speed and force of a player's volley as is the use of quality equipment.
This is a tempting choice. If lessons ARE as effective at improving the speed and force of a player's volley as is the use of quality equipment, as a tennis amateur who wants to potentially improve his or her game, you would either take classes/lessons OR use quality equipment.
However, the author's conclusion is NOT affected by this statement whether lessons can OR cannot be as effective as using quality equipment at improving your speed and force; the point is WE'RE MISSING THE POINT.
Is improving your speed and force key to raising your tennis game? That's not what this statement can help us answer, nor bridge the premise to the conclusion ---> Not sufficient.