参考答案：A

解析： There’s no doubt that athletes are playing hard enough to suppress immune defenses. The normal population in Australia expects to get between three and four upper respiratory infections each year. But if you look at groups of elite athletes, about 15 percent of those athletes can have six or seven or more, even up to 11 or They seem to get more vulnerable as they train harder.比较结构的表达和判断。原文中关于得呼吸道感染的比较表达有两处：1)The normal population…get between three and four...而运动员，尤其是优秀运动品却“have six or seven or more，even up to 11 or l2”，由此可见，优秀运动员的得病机率更高；2)They seem to get more vulnerable as they train harder．即“这些运动员们训练得越刻苦，身体越脆弱”。从这两处都可推测出题干的说法是错误的。 注意：1)熟悉比较结构的表达法。表示比较的手段很多，可以通过固定结构，也可通过统计数字作对比；2)掌握信号词，判断上下文逻辑关系，有助于迅速解题，如原文在说明普通人群得呼吸道感染的机率后使用了单词but，表明后面的对象的事实肯定与前面不一样，从该词的使用，也可猜测出优秀运动员得病的机率更高。