Ⅰ.单句语法填空
1．(2019·全国卷Ⅰ)Scientists have responded by noting that hungry bears may be congregating (聚集) around human settlements, leading to the illusion (错觉) that populations are higher (high) than they actually are.
解析：根据句中的than可知，此处应用形容词比较级。
2．(2018·全国卷Ⅰ)According to a review of evidence in a medical journal, runners live three years longer (long) than nonrunners.
解析：根据空后的than和语境可知，此处应该使用副词比较级形式，故填longer。
3．(2018·全国卷Ⅲ)He screams the loudest (loud) of all.
解析：根据空前的the以及空后的of all可知此处应用副词最高级。
4．(2018·浙江卷)There could be an even higher (high) cost on your health.
解析：此处表示这么做可能还会让你付出更高的健康代价。根据even可判断，此处要用形容词的比较级。
