本单元的功能项目是谈论过去和现在的时间关系 ;语法项目是现在完成时的另一种用法 :表示过去已开始 ,延续到现在的动作或状态 ;话题是“使我们的世界变得更美”,描述该话题时必然要用到现在完成时、一般过去时和一般现在时。这样 ,本单元的话题、语法和功能很自然地结合在一起 The functional items of this unit are to talk about the relationship between the past and the present; the grammar project is another use when it is completed now: it means that the past has begun and continues to the present action or state; the topic is “to make our world more beautiful. "When describing this topic, we must use the present time of completion, the past tense, and the present tense. In this way, the topics, syntax, and functions of this unit are naturally combined