This is possible because when a star dies, it basically expands to its maximum (explodes). Therefore, the materials of the exploded star mix with the primeval hydrogen of the Universe. Later, other stars are formed out of this mixture. Thats also how the sun was formed. :)
In an oligopoly type of market, there are only few producers whom dominate the market. This is the market type wherein there are only small number of firms that control the majority of the market share. The opposite to Perfect Competition, wherein there are unlimited number of producers. In an oligopoly, since there are only a few numbers competitors, each firm is likely to be aware of each other's action.
Deforestation because without trees and plants, they are nothing to convert CO2 into Oxygen.
