What characterizes "Dunning by Dunning Procedure” and “Dunning by Collection Strategy”?

What characterizes "Dunning by Dunning Procedure” and “Dunning by Collection Strategy”?
A . Both “Dunning by Dunning Procedure” and “Dunning by Collection Strategy” are based on a rules engine which determines the next step.
B. “Dunning by Dunning Procedure” is based on number and sequence of dunning levels, while “Dunning by Collection Strategy” is based on a rules engine which determines the next step.
C. “Dunning by Dunning Procedure” is based on a rules engine which determines the next step, while “Dunning by Collection Strategy” is based on number and sequence of dunning level.
D. Both “Dunning by Dunning Procedure” and “Dunning by Collection Strategy” are based on number and sequence of dunning levels.

Answer: B