I believe the correct answer is A. Increases the rate of a chemical reaction. This is because they act as catalysts.
This is only one part of the answer, but its important: high-altitude O2 absorbs much energy from the sun (including radioactivity), which forms the ozone layer. this process protects delicate molecules important to life - most notably dna
Microorganisms that are capable of causing disease are called pathogens. Although microorganisms that cause disease often receive the most attention, it is important to note that most microorganisms do not cause disease. In fact, many probably provide some protection against harmful microorganisms because they effectively compete with the harmful organisms for resources, preventing them from growing.
