In the library,I found a useful book____how to use English grammar.
问题描述：
In the library,I found a useful book____how to use English grammar.
答案为hanving explained,为什么
答
have 加ing 分词形式作为定语,修饰book
在图书馆,我看到一本解释着如何使用英语语法的有用的书.