《石油工程专业英语》P51 Decide whether the following statements are true ( T ) or false ( F ) according to the text. 1) Crude oil on the surface is thicker than that in subsurface rock. 2) Most crude oils are lighter than water. 3) API gravities vary with increasing density of oil. 4) Hydrocarbons are compounds consisting of carbon and hydrogen elements. 5) With decreasing boiling point the paraffin fraction of oils gradually increases. 6) The hydrocarbons in crude oil are liquid at normal temperatures and pressures. 7) The oxygen compounds found in crude oil include acids, ketones, phenols, and alcohols.