Complex sentence: Oil is generally a product of thermal breakdown of type I and type II kerogen during catagenesis, thus its D content should reflect both source kerogen signal, generation fractionation, isotopic exchange and other maturation effects.
Split into simpler sentences: Oil is generally a product of thermal breakdown of type I and type II kerogen during catagenesis. The deuterium content should reflect the source kerogen signal, generation fractionation, isotopic exchange and other maturation effects.