Which of the Following Was Not Listed as a Principle

Which of the following was not listed as a principle that applies to setting up categories to manage rates at a hotel?

A) Each category should have a reasonable volume of activity.
B) Limit the total number of transient rate categories to no more than six or so.
C) Group business should have a separate hierarchy of buckets to allow the operator to track pickups of room blocks.
D) All of the above were listed in the article.
E) Only a and c were listed in the article