Critical Reasoning

According to some sports historians, professional tennis players develop unique playing styles that result from a combination of the peculiarities of each player's physical attributes and the influence of coaches during their early adaptation to the game. But when the increase in strength and endurance of modem players is discounted, it becomes readily apparent that the playing styles of the current crop of professional tennis players are no different from the styles of players from previous generations. Clearly, there is a universally efficient tennis style to which all professional tennis players conform.

The argument above is most weakened by which of the following statements?

(A) The differences in physical attributes among tennis players are even more pronounced than the sports historians believe.

(B) Few current professional tennis players are familiar with the professional tennis players of fifty years ago.

(C) The increased strength of current tennis players contributes more to the development of individual playing styles than does increased endurance.

(D) All of the early coaches of today's professional tennis players were professional tennis players themselves earlier in their lives.

(E) Weight training and greater attention to diet are the primary factors in the increased strength and stamina of the current generation of professional tennis players.

OA: D

I believe that this is a cause and effect reasoning and it can be weaken by alternate cause. The same thing is in D but I could not understood why D is fitting for this. Can some explain about it?