How do microorganisms affect humus and thereby soil health?a.The presence of any microorganisms causes the destruction of humus, which leads to a reduction in soil health.b.Microorganisms increase the production of humus, which leads to a decrease in soil health.c.Microorganisms increase the production of humus, which leads to an increase in soil health.d.Microorganisms exist independently of humus and therefore do not affect soil health.