Read this excerpt from the preface of a book written about machines. I have been fascinated by machines since I was a child. Playing in the creek behind my house, I used sticks, string, and plastic cups to create a pulley system for drawing up water. When I got older, my friends and I built ramps for our bikes, and sped down them with abandon. It was only natural that I became an engineer who designs machines for all sorts of tasks. Based on this excerpt from the preface, which best explains why the author wrote the book? The author used materials found around the house to make simple machines. The childhood friends of the author were also interested in making and using machines. The author has had a lifelong interest in machines and how to develop them for a variety of purposes. As a child, the author enjoyed outdoor activities such as playing in a creek and riding on a bik