The nutrient cycles between the living and nonliving parts of an ecosystem are called______________.（ ） A: physical cycles B: chemical cycles C: Biogeochemical Cycles D: biological cycle

The material flow can be divided into the following ( ) two categories according to whether the material flow is mainly caused by human activity A: Material biogeochemical flow and its anthropogenic flow B: Material flowing with the atmosphere and with the water body C: Material industrial and agricultural flows D: Material industry flow and consumption flow