Mrs. Gibson, the president of the garden club, has written a book called Leaf by Leaf. The book includes close-up photographs of leaves found on local trees. The pictures are very useful in identifying the kind of trees you have in your backyard. What is the author's purpose for writing Leaf by Leaf? A) To sell her photographs of trees. B) To explain how to build a tree house. C) To help readers identify a tree by its leaves. D) To entertain the reader with stories about squirrels.