In cells capable of cellular respiration in a step often called the transition or bridge reaction, one is transported to the site the Krebs cycle by a large carrier molecule called . This step is important because it results in one complete "turn" of the cycle and the production of molecules from the Krebs cycle that can then be used in the electron transport chain.

Which of the following statements is most likely correct about a rock belonging to the jurassic age and a rock belonging to the cambrian age? options: 1) they have identical fossils of organisms that have evolved over time. 2) both have animal fossils preserved in them due to weathering and erosion. 3) they contain different fossils because life on earth has changed through time. 4) the fossils in them were formed on the surface of earth due to exposure to sunlight.