Final answer:
Geographers use physical elements like climate, vegetation, and river systems from physical geography to define world regions. Language and religion are human factors, and precipitation is a physical factor used for such definitions.
Step-by-step explanation:
When a geographer uses physical geography to define world regions, they would primarily consider physical elements such as climate, vegetation, and river systems.
Therefore, the correct answer to which moniker may be used is C. Precipitation. Language and religion are considered human factors and while they are critical when analyzing human geography, they are not typically used in the context of physical geography.