What have people discovered about hobbies?Hobbies can be profitable and ______

Many people have discovered that(Q11)hobbies can be profitable as well as fun. Some people have fine collections of bottles, flags, stamps or even match boxes. (Q12)Painting, writing and taking photographs are examples of hobbies that may become occupations. Every writer, artist and photographer probably started as a hobbyist before becoming a professional. Many doctors believe that hobbies help to(Q13)make our lives more enjoyable. They believe that people who raise fish or collect records are too busy to spend their time worrying. Doctors also think(Q14)that an active person, such as a football player, should have a restful hobby such as reading, while(Q15)a person who sits at a desk all day should have a lively hobby such as tennis, golf or swimming. Most people in the United States agree with the doctors. It is difficult to find an American who does not have a favorite hobby.
Q11: What have people discovered about hobbies?