In 2007, the Price of Oil Increased, Which in Turn

In 2007, the price of oil increased, which in turn caused the price of natural gas to rise. This can best be explained by saying that oil and natural gas are

A) complementary goods, and the higher price for oil increased the demand for natural gas.
B) substitute goods, and the higher price for oil increased the demand for natural gas.
C) complementary goods, and the higher price for oil decreased the supply of natural gas.
D) substitute goods, and the higher price for oil decreased the supply of natural gas.