Which If the Following Is True About a Soil Quality

Which if the following is true about a soil quality index (SQI) ?

A) The SQI must be related to a particular functional goal for the soil in the ecosystem.
B) Soil pH,bulk denisty (Mg m^-3) and soil active C levels (mg kg^-1) may all be averaged together in a SQI.
C) Soil quality indices may be used to monitor the effects of changes in soil management practice over time.
D) All of the above are true.
E) None of the above are true.