it is difficult to learn all day.一天都在学习是件困难的事
it is easy for me to swim in the pool!在游泳池游泳对我来说是件容易的事
it is impolite to speak with the mouth full!当嘴里被塞满（食物）的时候说话时间很没有礼貌的是.
用difficult,easy,impolite,it作形式主语,不定式作真正主语,各造3个句子翻译,
it is difficult to learn all day.一天都在学习是件困难的事
it is easy for me to swim in the pool!在游泳池游泳对我来说是件容易的事
it is impolite to speak with the mouth full!当嘴里被塞满（食物）的时候说话时间很没有礼貌的是.