【单选题】You could also try to persuade them to use recycled _____.
【单选题】We are going to ______ to buy some rulers.
【简答题】普通平键联接的主要失效形式是_______________,导向平键联接的主要失效形式是__________。
【单选题】I went to ____ to buy a ruler and a rubber.
【简答题】普通平键联接的主要失效形式是__,导向平键联接的主要失效形式__。