题目

Children who spend more time outdoors may have a lower risk of becoming nearsighted, new research suggests. In the study, researchers looked at about 1,900 schoolchildren. The scientists found that the kids who had been instructed to spend more time outdoors over three years were 23 percent less likely to develop nearsightedness during this time than those who had not been instructed to spend more time outdoors. Moreover, among the kids who did become nearsighted during the study, the degree to which their eyesight worsened was slightly smaller among those who spent more time outdoors. When they reached the burning building the firefighters found that their ladders were ______________ to reach the people who were trapped. [    ] A. long enough　　 B. short enough C. not long enough D. too long