题目

      A recent study suggested that taking a bottle of water into the exam hall could help students improve their grades.        According to the study those who brought drinks,   71     (especial) water, with them when sitting their exams performed up to 10 per cent better than those who did not.       Comparing their exam results with their normal schoolwork grades, scientists then found that all those who       72      (bring) drinks with them got better grades     73      between 2 and 10 percent.       It is unclear     74  11．在比例尺1：10的图纸上，甲乙两个正方形的边长比是2：3，那么甲乙两个正方形实际的面积比是（　　）A．1：10B．2：3C．4：6D．4：9