About 300 million years ago, the seas and oceans were inhabited by tiny plants and other organisms. these organisms died and were buried on the ocean floor. over time, their bodies were covered with silt and mud that was rich in organic material, forming layers of organic matter. this matter was subjected to high temperature and pressure. in such conditions, oxygen was available in abundance. over a period of many years, the matter decomposed and formed oil and gas. which sentence is incorrect

The formation of petroleum takes place because of various chemical reactions, which take place to the substances that were once living. In the majority of the cases, the formation of liquid petroleum takes place from the algae and zooplankton, which get settled to the bottom of the lake or sea, and was then got buried underneath the sediments.  

The sediment makes sure that no oxygen could reach the dead and decaying organic matter, and thus, the stage gets set for the production of oil. In the majority of the cases, the organic matter goes via many modifications, which take millions of years. The sediments continue to pile over each other and enhance the pressure on the organic matter, this leads to the formation of natural gas and liquid petroleum.  

Thus, the sentence, that is, "In such conditions, oxygen was available in abundance" is the incorrect one.  

1: most common garden plants prefer loam — soils with a balance of different-sized mineral particles (approximately 40% sand, 40% silt, and 20% clay) with ample organic matter and pore space. however, some plants grow better in sandy soils, while others are well-adapted to clay soils.

2: available water capacity is the maximum amount of plant available water a soil can provide. it is an indicator of a soil's ability to retain water and make it sufficiently available for plant use. available water capacity is the water held in soil between its field capacity and permanent wilting point.

3: it is the same for all living things (plants and animals). it also includes very tiny organisms that our eyes cannot see. they are known as microorganisms, and include viruses, bacteria and fungi.