What factors keep an ecosystem going?

Time, interface, &sequence; What ever the composition of the system, be it static (balanced) or dynamic (subject to change) it exists because of the dimensions that govern its composition. Time = a physical measurement of the expenditure of energy. Interface= each component reaching for dominance, verses all other components seeking to achieve the same result, thus achieving a compromise, or balance. Sequence= each event measured in milliseconds, or nanoseconds, or what ever increment of stability is achieved, until balance succeeds.

The answer is option b.

Humans can affect weathering and erosion in several ways.  humans cause  increases in acid rain and pollution, which increase the amount of  weathering  agents in the air and water, and then on land.for an easy answer: 1) acid rain2) pollution