In the library, I found a useful book how to use English grammar.
A. to explain
B. explained
C. having explained
D. explaining
网友回答
A. to explain
B. explained
C. having explained
(答案→)D. explaining
解析：考查现在分词做定语，因为book和explain是主动关系，用现在分词做定语，句意是：在图书馆，我发现一本有用的解释怎么使用英语语法的书。选D。