GWD 21-33 B
One of the limiting factors in human physical performance is the amount of oxygen that is absorbed by the muscles from the bloodstream. Accordingly, entrepreneurs have begun selling at gymnasiums and health clubs bottles of drinking water, labeled “SuperOXY,” that has extra oxygen dissolved in the water. Such water would be useless in improving physical performance, however, since the only way to get oxygen into the bloodstream so that it can be absorbed bye the muscles is through the lungs.
Which of the following, if true, would serve the same function in the argument as the statement in boldface?
A. the water lost in exercising can be replaced with ordinary tap water
B. the amount of oxygen in the blood of people who are exercising is already more than the muscle can absorb
C. world-class athletes turn in record performance without such water
D. frequent physical exercise increases the body’s ability to take in and use oxygen (A)
E. lack of oxygen is not the only factor limiting human physical performance
问same function, 需要和原文一样作为原因，支持Such water would be useless in improving physical performance；
答案为A，说“运动中流失的水份可以通过日常的TAP WATER补充”，说明运动需要补充水，那么这种SuperOXY的水也可以补充；但是补充水中的氧气能否被身体吸收，增加performance不得而知，所以不能支持也不能削弱水无用的结论；
答案B，说“运动的人血液内的氧气含量已经超过了肌肉可以吸收的含量”，正好说明其他增氧方式都是无用的，支持了结论。
因此，认为答案应该为B，请指教。 | 
