I'll give the book to him if he _______ here next Sunday.  

阅读下面材料, 在空白处填入适当的内容(一个单词)或括号内单词的正确形式。将答案填写在答题卷的相应位置。

    Everyone seems____(have) his or her own holiday. Dad has Father's Day. Mom has Mother's Day. Children have Children's Day. ____(lover)have Valentine's Day. But is there a special day____older people?

Of course. The Chongyang Festival is the holiday when Chinese people show love for their____（old）. Celebrated on the ninth day of the ninth lunar month, the festival is also known as the Double Ninth Festival. Nine is the____(high) digit(数字), so it____(regard)that the two together mean a long life.

The festival comes ____the golden time of autumn. The clear weather and the joy of harvest make for a happy atmosphere. On the day, people____(traditional)climb a mountain and carry dogwood(茱萸). People in ancient times believed____the plant could drive away evil____(spirit) and prevent people against cold in winter.

如图所示，用“碰撞实验器”可以验证动量守恒定律，即研究两个小球在轨道水平部分碰撞前后的动量关系．