Which element's cycle depends on kinds of bacteria to keep the element available to other organisms?
a. carbon
b. hydrogen
c. nitrogen
d. phosphorus

Which best describes the scientific method? a. a path of clearly defined steps that must be followed in a particular order b. a possible answer to a scientific question based on knowledge or research c. the recipe for how to conduct an experiment that must be followed precisely d. the process of hypothesis and testing through which scientific inquiry occurs