B

Reasoning: Any suitable population distribution (e.g., World Standard, pooled study populations, census data from a chosen year) can be used as the standard; it is not obligatory to use the national population. Direct standardization uses the study population’s age-specific rates applied to the age structure of the chosen standard, whereas indirect standardization applies the standard population’s age-specific rates to the study population’s age structure, making the other statements correct [Naing, 2000, PMID 22844209].