Work index is defined as the_________________?

A. Gross energy (kWh/ton of feed) needed to reduce very large feed to such a size that 80% of
the product passes through a 100 micron screen
B. Energy needed to crush one tonne of feed to 200 microns
C. Energy (kWh/ton of feed) needed to crush small feed to such a size that 80% of the product
passes a 200 mesh screen
D. Energy needed to crush one ton of feed to 100 microns