诗中“牛马”、“春风”、“野草”等词都含有某种寓意和寄托，说说它们的象征意义是什么。

用方框中所给单词的适当形式填空。

         As we know, there are many beautiful places in China, such as Hong Kong, Harbin. They attract a lot of people at home and abroad. But it's hard for ____ to choose where they can go. You can tell them ____ Guide to China, which ____ China in detail. If they have no chance to go through the book, you may show them advertisements for traveling, then after ____, they can decide where to go. They will have a good trip and take photos in ____ of it.

计算（a⁶b³）÷（2a³b²）的结果是（　　）

铁的使用非常广泛，但较容易生锈。