The bicycle is one of the simplest yet most useful inventions in the world.  What is most surprising is that it was not ____________earlier, although the great inventor Leonardo da Vinci had drawn pictures for bicycles and also for flying machines and some other things. Those things were not made ____________he died.

A person riding a bicycle uses much energy ro make the bicycle move, and there is no pollution at all when you are riding. Even so, in developed____________, most people don’t travel to work by bicycle. It is not because the bicycles are expensive or people feel____________if they ride to work. It’s because ____________cars on the roads becomes larger. It certainly becomes ____________ to ride a bicycle. As a result, more people put their bicycles away and go to work in their cars and in this way, the situation is made more serious.____________the best way to make riding safer and more popular is to create paths only for bicycles.