Guidelines (rules-of-thumb) are general standards of comparison developed from:

A) Industry guidelines.
B) Past experience.
C) Analysis of competitors.
D) Relations between financial items.
E) Dun and Bradstreet.

Guidelines or rules-of-thumb are generally based on past experience and observations. They may not be standardized or industry-specific, but are often used as a starting point for decision-making. Analysis of competitors and relations between financial items can also provide benchmarks for comparison, but they are not the primary source for developing guidelines. Dun and Bradstreet is a business information and credit reporting company and does not typically provide guidelines.