题目

About one in ten computer game players show signs of addictive behavior that      have negative effects on their family, friends and school work , according to a new study. A． could       B．should      C．need            D．would   答案：A  此题考查情态动词的用法. could 表示”可能性”  如图是余江同学自制的简易净水器．（1）净水器中活性炭的作用是 ；（2）你有同样的感受吗？说说它的净化效果．