Many men tried to fly like birds. They made wings for themselves, usually of feather tried to fly (1)______ moving their arms as a bird (2)______ None of them was successful. A bird has a very light body but very strong wing muscles. A man on the contrary has a (3)______ body not very strong arm muscles. A man will never fly like a bird. His muscles are not (4)______. He can only fly properly in a plane with an engine. There is a kind of plane that doesn't have an engine. It (5)______ a glider. It's pulled into the air, rather like (6)______ a kite. If there is a good wind, it can (7)______ into the air sometimes cover long distances. Some men didn’t find sitting in a glider (8)______. They wanted to glide by (9)______ wings, like the "bird men" of old time. But the wings of the modern "bird men" were different. They were straight strong. They weren’t (10)______ feathers.

1. A. by B. through C. with D. in