13. Krebs Cycle and ETC require oxygen to occur, making them?

Acetyl CoA is produced during the process of Krebs cycle in the presence of oxygen.

Explanation:

Krebs cycle is also called citric acid cycle. This process is used by living organisms for the release of energy from food molecules in the process of aerobic respiration. In this chemical reaction, oxidation of acetyl-CoA occurs which is obtained from food molecules such as carbohydrates, proteins and lipids. When oxidation of food molecules occurs, energy is released in the form of Adenine tri phosphate (ATP) and carbondioxide gas is produced.

feral cats are estimated to eat tens of millions of native animals each night in australia

the earth is thought to have been formed about 4.6 billion years ago by collisions from a cloud of hydrogen, helium, rock, ice and other materials. these were pulled together by gravity to form objects in and around earth like- asteroids and small early planets called planetesimals.

so, the best possible answer to this question will be option d- to harden materials to form different parts of earth’s layers