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

Wind energy is plentiful in regions with vast open spaces it is a non polluting renewable resource what could be an economic factor that makes the use of this resource less feasible then non renewable resource even in such regions

The breakdown of food is accomplished by enzymes. a. physical b. chemical c. mechanical d. none of the above

49 ! how are energy cycles and growth cycles related?