Why is B incorrect?

@Ryan, B has no impact on the validity of the conclusion. Even if rubber was used for other purposes from 1000 to 1518, a year before Cortez's observation, it does not tell us anything about when the game must have originated.

Understood, thank you.

How come the negation of "The game had been played since its inception with a rubber ball" is "not necessarily played" instead of just "not played." To be more clear, why is it #1 and not #2? 1. The game had not necessarily been played since its inception with a rubber ball. 2. The game had not been played since its inception with a rubber ball.

Hi Salvatore, I generally like to go with the weakest possible negation, and the #1 feels like the weaker statement. If we think that the game had not been played with a rubber ball since its inception, that would imply that from the time it was invented until Cortez showed up, it was not played with a rubber ball, and then everyone suddenly decided to start using rubber. Your #1 allows for much more flexibility. We are negating a statement that equates to an "always." We do not have to assume the negation of always is never (which is your #2), but rather we could simply say "not always" which is your number 1.