What is a fossil? the remains of an animal or plant preserved within a layer of rock a large body of compacted ice formed over thousands of years the energy radiated from the sun a change in the structure of earth's surface

The remains of an animal or plant preserved within a layer of rock

Fossils can be defined as the remains of plant or animal, their imprints and traces of their activities that are preserved in the layer of sedimentary rocks.

an active site is a region that is present on an enzyme where the reactants or the substrate molecules we can say bind and experience a chemical reaction. the substrate is basically a reactant whose concentration is changing and that is converting into a product after binding at the active site of an enzyme

the answer is lactic acid from anaerobic respiration. the acid in lactic acid is what creates sore and burning muscles. if you think about how acid burns that will give you a clue for questions like this.