B is the correct answer because all the classes are hierarchy’s in a sense
Microbes. Bacteria, for example, convert nitrogen and carbon dioxide from the air into usable components that plants and animals can use as essential building blocks. A loss of all microbes would be terrible news for living organisms that can't create or take in these essential nutrients on their own.
Evolution Due to environmental factors, It may not look it, but, needles are leaves, they collect solar radiation to produce glucose through the process of photosynthesis, however, needles are, some would say, evolutionary superior to leaves. Needles themselves hold in more water due to their dense wax coating, they are very difficult for insects and other organisms to eat, one because of their structure, and two because of their acidity, they can catch sunlight all year long due to their winter resilience( they don't fall, during the winter), and they have less surface area for wind to catch, which leaves them better protected from wind than most deciduous trees, however the surface area can also pose a larger problem for less surface area means less sunlight interception, therefore more are needed to compete against regular leaves. But.. I Digress... Plant needles are 'PROBABLY' initially the result of evolution of narrow leaves due to climate or environmental factors.
Sry its so long got carried away! Hope this helps xD
Density-dependent limiting factors cause a population's per capita growth rate to change—typically, to drop—with increasing population density
