A BRIDGE

As a bridge plays a very important role for connecting one area and another area by providing a way for people, animals and vehicles across a river, canal, railway, or others alike, people and government have been building many types of bridges; from the very simple and cheap until the very expensive and sophisticated ones.
In small villages, bridges are usually only made of bamboos or logs. Of course, they are not strong enough but still very useful. They are used mostly by people and small animals like sheep. The heaviest burdens are perhaps farmer carrying fruit or vegetables on their shoulders. They go to the markets to sell their fruits or vegetables from their gardens. Big animals like cows or buffaloes usually pas under these bridges because the shepherds know that bridges can not bear too heavy burdens, besides can bathe their cattle in the river while driving them back home.
While the bridges in small towns or in agriculture areas where the people need car or small trucks to transport their crops to towns in harvesting season are usually concrete bridges which are made from cement, coarse aggregate (stones and gravel), fine aggregate (sand ) and water. These bridges are certainly much stronger than bamboo or wooden and they can bear much heavier burdens. Cars and trucks can pass over these bridges.
In cities or areas where many big and large vehicles pass by, the bridges are not only made of concrete but also steel. The examples of these bridges are a steel arch bridge, a suspension bridges,a bailey bridges,and so on. Buildings these kinds of bridges need a quantity or money and sophisticated technology. But most people will be able to benefit from this investment a relatively long time.