Because of the trade embargo, the price of gasoline was rising dramatically.
Because there was the trade embargo, the price of gasoline was rising dramatically.
Because of the trade embargo, the price of gasoline was rising dramatically.
Because there was the trade embargo, the price of gasoline was rising dramatically.
The preposition "because of" is designed for discussing a cause that is a single noun, such as "trade embargo." The GMAT disapproves of creating a long awkward "there" statement in order to turn the noun into a clause so we can use "because of" rather than "because."