The correct answer is A.
Muscles need energy to produce contractions. The energy is derived from ATP (which stands for adenosine triphosphate) that is present in muscle cells.
Muscles tend to contain only limited quantities of ATP. When depleted, ATP needs to be resynthesized from other sources namely creatine phosphate (CP) and muscle glycogen. Other supplies of glycogen are stored in the liver. The body is also able to resynthesize ATP from lipids, i.e. free fatty acids. Different sources of energy are used depending on intensity and duration of the workload .
35. The paragraph at the top of the page tells you "Catalase [is] a biological catalyst produced by cells [that] speeds the breakdown of hydrogen peroxide."
Of course, you know that, in general, a catalyst is a substance that facilitates a chemical reaction without being used up as a result of that reaction.
36. Catalase is most active at the temperature of 35 °C. (This is not unexpected, as 35 °C is near the temperature considered to be normal body temperature (37 °C).) The table and the corresponding graph show this to be the case.
Nitrogen fixers are bacteria
Studying fossils allowed researchers to learn about organisms that lived long ago. The fossils provide as evolutionary evidence that shows how organisms in our present time have evolved over time and which common ancestors they are tied to. Fossils also provide information about climate change depending on the region and location they are found in. Fossils also date back to millenias ago, so fossils dated very far back in the past can help researchers infer that life had existed even farther than what they might have discovered. And finally, by studying fossils, you can determine how the organism may have died.