Nowdays, enery is important to every country. There are few places to extract oil. Only a few countries have gasoline in their territories, such as Russia, Iraq, Dubai. In addition, there are some political facotrs of export which lead to high gasoline prices. Secondly, the transportantion of oil is very difficult and cruiese or pipelines are usually used. There might be some problems about cruiese transportation. In the process of transportation, it is also expensive. Although the construction of pipelines can be used for a long time, the amount of work is large and the maintenance cost is very high. Finally, because of the scarcity of resources and the international sitatuation, some countries debilberately raised oil price to purachse and rise their competetion as well. Thus it might suppress ohter countrise.