Over time the oil and natural gas worked its way upward through the earth s crust and this is were the most oil and natural gas resources can be found today (How Fossil Fuels Formed).
(oil and natural gas; worked upward; T:Over time) (this; is; ) (Fossil Fuels; Formed; )
oil and natural gas this Fossil Fuels
worked upward is Formed
T:Over time