题目

(2018·全国卷Ⅱ)Diets have changed in China—and so too has its top crop. Since 2011, the country __1__ (grow)more corn than rice. Corn production has jumped nearly 125 percent over __2__ past 25 years, while rice has increased only 7 percent. A taste for meat is __3__ (actual) behind the change: An important part of its corn is used to feed chickens, pigs, and cattle. Another reason for corn's rise: The government encourages farmers to grow corn instead of rice __4__ (improve) water quality. Corn uses less water __5__ rice and creates less fertilizer (化肥) runoff. This switch h为探究“温度对唾液淀粉酶催化作用的影响”，小丽同学设计了如下实验：步骤一：收集唾液并与蒸馏水按1：1的体积比制成唾液稀释液；步骤二：取可溶性淀粉1克，放入烧杯中，加入99毫升蒸馏水，搅拌，缓慢加热，溶解，制成1%的淀粉溶液并冷却至室温；步骤三：取4支洁净的试管编上号，按表中物质的量依次加入各试管并振荡，放置在一定温度下的水浴中保存10分钟；步骤四：取出试管，分别滴加1滴体积分数为0.4%碘酒溶液，然后摇匀，观察并记录各试管中溶液颜色的变化情况如表，（1）设置A组实验的目的是______；（2）收集唾液的方法是______；（3）根据实验记录分析，实验结果所支持的实验假设是______ 试管编号 A B C D 加入物质 淀粉溶液/毫升 4 4 4 4 蒸馏水/毫升 2 0 0 0 唾稀释液液/毫升 0 2 2 2 保存温度/℃ 37 37 100 0 保存时间/分 10 10 10 10 溶液颜色 变蓝 不变蓝 变蓝 变蓝