Which of the following statements about biogeochemical cycles is not true?
a. biogeochemical cycles include living and nonliving elements.
b. the rock cycle is a biogeochemical cycle.
c. biogeochemical cycles are an important part of the earth system.
d. carbon, nitrogen, and oxygen cycles are biogeochemical cycles.

The carbon cycle is definitely an example for a biogeochemical cycle -  The nitrogen and oxygen cycles are biogeochemical cycles too! so the last statement is true.

The biogeochemical cycle includes also for example the movement of water which is nonliving, so a) is also true.
The false statement is b) since the rock cycle does not include any biomatter.

Ithink the answer is true