Based on this excerpt from the preface, which best
explains why the author wrote the book?
O The author used materials found around the house to
make simple machines.
O The childhood friends of the author were also interested
in making and using machines.
O The author has had a lifelong interest in machines and
how to develop them for a variety of purposes.
O As a child, the author enjoyed outdoor activities such as
playing in a creek and riding on a bike.