The basic ingredients from which cement is made are both cheap and plentiful. Materials as common as limestone and clay will do. Nevertheless, the price of cement is influenced by the price of oil, because turning the basic ingredients into cement in high-temperature kilns uses large amounts of energy. Which one of the following can be logically inferred from the passage? ['Whenever oil prices rise, cement prices drop.', 'Oil is a source of energy for some of the kilns used in the making of cement.', 'The higher the price of cement rises, the higher the price of clay rises.', 'Oil is one of the basic ingredients that make up cement.']