関連ワード:  why is petroleum known as fossil fuel    why is petroleum called as fossil fuel    why is oil referred to as fossil fuel    why is coal and petroleum known as fossil fuels    why is crude oil known as fossil fuel    why is petroleum called fossil fuel class 8    why is petroleum called fossil fuel class 7    why is petroleum called fossil fuel class 5    why is petroleum called fossil fuel short answer    why is petroleum called fossil fuel  
結果 : why is petroleum known as fossil fuel