The Term "Crude" in Reference to Birth and Death Rates

The term "crude" in reference to birth and death rates means that:

A) in comparing birth and death rates for different nations, one must keep in mind that some governments are more likely to lie than others
B) they compare the total number of deaths with the total midyear population
C) population change through immigration is not included in the calculation
D) such statistics are rough estimates and are highly inaccurate