Answer:
Front
Explanation:
When two air masses collide, a front is formed. The two most common types of fronts are cold fronts and warm fronts.
Cold fronts are formed by the advance of cold continental polar or continental arctic air towards the south. The colder air wedges underneath the warmer air mass to the south and causes it to rise, forming a storm front.
A warm front is the pushing action done by an advancing mass of maritime tropical warm and moist air that pushes a colder air mass out of the way by rising on top of it gradually and moving it away slowly. This causes an extensive cloud front of light rains.
States create their own laws, states have their own constitution, land and county governments. The state law stands unless a federal law overwrites it. States have their own transportation departments (make the roads, plan the roads, repair the roads).
World War I and II. These wars caused lots of economic growth and development because there was a pressure to create better inventions. Having better technology could mean the win or lose of a war. :D